Received: 25 March 2020 DOI: 10.1111/grow.12430 | Revised: 28 July 2020 | Accepted: 11 August 2020 ORIGINAL ARTICLE The heterogeneity of agglomeration effect: Evidence from Chinese cities Wenwen Wang1,2 1 School of Finance, Zhejiang University of Finance & Economics, Hangzhou, China 2 School of Economics, Zhejiang University, Hangzhou, China Correspondence Wenwen Wang, School of Finance, Zhejiang University of Finance & Economics, No. 18, Xueyuan Street, Xiasha Higher Education Park, 310018 Hangzhou, China. Email: wangwendy2018hi@gmail.com Funding information Research for this project was supported by Zhejiang Institute of Social Science and Technology Planning Office under Grant (number19NDQN339YB) and Management Office of the National Statistical Scientific Research Organization of China under Grant (number 2017LY06) | 1 Abstract Using annual surveys of industrial firms in China from 1998 to 2007, this paper applies the non-linear least squares (NLS) method based on a grid search to analyse the effect of city size on firm total factor productivity (TFP). The results show that overall, the agglomeration effects in large cities, but not selection effects, significantly promote improvement in firm TFP. The optimal agglomeration scales of different industries differ as follows: those of capital- and technology-intensive industries are larger than those of labour-intensive industries. The agglomeration effects are also robust to different spatial areas without considering administrative boundaries. An inverted U-shaped relationship exists between firm size and agglomeration effects, while the relationship between firm age and agglomeration effects is U-shaped. State-owned firms experience weaker agglomeration effects than nonstate-owned firms. Cities higher in the administrative hierarchy and those with special economic zones have stronger agglomeration effects. However, cities higher in the administrative hierarchy and those with a larger economic development zone index can provide more resources to increase the survival rate of low-productivity firms; thus, selection effects are not significant in Chinese cities. IN T RO D U C T ION Industrial agglomeration is regarded as the most important engine for industrial growth in developing countries (Badr et al., 2019). Numerous studies have shown that industrial agglomeration contributes to improvement in regional productivity (Andersson & Lööf, 2011; Badr et al., 2019; Ciccone, 2002; 392 | © 2020 Wiley Periodicals LLC. wileyonlinelibrary.com/journal/grow Growth and Change. 2021;52:392–424. | 393 Ke, 2010; Liang & Goetz, 2018). Scholars have found that co-agglomeration plays an important role in economic spillover and promotes growth (Aleksandrova et al., 2020; Ellison et al., 2010). However, the debate in the academic community regarding whether agglomeration effects are caused by intra-industry agglomeration (localization economies) or inter-industry agglomeration (urbanization economies) has continued (Barufi et al., 2016; Cainelli et al., 2015; Fazio & Maltese, 2015; Glaeser et al., 1992). In recent years, scholars have begun to emphasize the differences in agglomeration effects among different industries and firms with different characteristics (Amara & Thabet, 2019; Antonietti & Cainelli, 2011; Badr et al., 2019; Beaudry & Schiffauerova, 2009; Duschl et al., 2015; Hartog et al., 2012; Hu & Liang, 2008; Kenney & Patton, 2005; Liang & Goetz, 2018; Neffke et al., 2011; Tao et al., 2019). In addition, scholars have noted the heterogeneity of firms (Ottaviano, 2011) and proposed that uncontrolled firm selection effects could cause endogenous problems and the overestimation of agglomeration effects (Ciccone, 2002; Henderson, 2003; Rosenthal & Strange, 2004). Therefore, some studies combine agglomeration effects with selection effects and use data for empirical analyses (Arimoto et al., 2014; Baldwin & Okubo, 2006; Behrens et al., 2014; Cieลlik et al., 2018; Combes et al., 2012; Maré & Graham, 2013; Otsuka & Goto, 2015; Yu & Yang, 2014). However, few existing studies comprehensively evaluate the heterogeneity of agglomeration effects while considering selection effects. With fiscal decentralization and the economic growth-oriented promotion incentive institution (Cao et al., 1999; Li & Zhou, 2005; Montinola & Jackman, 2002), local governments compete to provide low-cost land and subsidize basic investment for manufacturing firms. Numerous industrial parks and economic development zones have been constructed through the transfer of industrial land at low prices. Areas with development zones have large advantages in attracting high-quality firms due to the cheap land, tax relief, and credit support (Lu et al., 2019) and can form a scientific industrial space layout in a targeted manner, affecting the agglomeration effects. However, many governmental supports prolong the survival of a series of low-productivity firms, which, in turn, could negatively affect the competition effects. In fact, there are numerous zombie firms in China (Wang et al., 2018). The existence of such firms has seriously affected the market mechanism of the survival of the fittest. Therefore, the development of agglomeration effects in China changes based on regional features, industry features, and firm features. These differences warrant further discussion. Based on the quantile approach proposed by Combes et al. (2012), this paper uses the non-linear least squares (NLS) method proposed by Yu and Yang (2014) to explore the influence of city size on firm TFP. By separating the selection effects, it is found that the agglomeration effects significantly promote improvement in firm TFP, while selection effects do not. Subsequently, this paper divides industries into capital- and technology-intensive industries and labour-intensive industries and finds that the optimal agglomeration scales of different industries differ. The agglomeration scales of capital- and technology-intensive industries are larger than those of labour-intensive industries. An inverted U-shaped relationship exists between the firm size and agglomeration effects, while a U-shaped relationship exists between the firm age and agglomeration effects. The agglomeration effects of state-owned firms are weaker than those of non-state-owned firms. Cities with higher administrative levels and cities with special economic zones have stronger agglomeration effects. In addition, this article further analyses the reasons why the selection effects are not significant. The contributions of this paper are as follows. First, this paper uses the NLS method based on a grid search to improve the quantile approach proposed by Combes et al. (2012), thereby reducing the degree of non-linearity in the optimization objective function and improving the operating efficiency. Second, this article further examines the heterogeneity of agglomeration effects among different industries, firms with different characteristics and regions with different amounts of resources. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG Analysing the differences in agglomeration effects from various perspectives helps provide a comprehensive understanding of agglomeration effects. Third, this paper uses a web crawler to locate the specific latitude and longitude of firms in a robustness test and uses ArcGIS to split space at different units, thereby alleviating the interference of the modifiable areal unit problem (MAUP). This paper proceeds as follows. Section 2 reviews the literature and proposes several hypotheses. Section 3 introduces the theoretical model and methodology. Section 4 reports the data source and variables. Section 5 reports the main regression results and several robustness checks. Finally, Section 6 draws the main conclusions. 2 | L IT E R AT U R E R E V IE W A N D RESEARCH HYPOTHESIS As the data change from macro level to micro level, the discussion regarding agglomeration effects changes from the regional level to firm level (Andersson & Lööf, 2011; Ciccone, 2002). Some scholars make a more detailed distinction between agglomeration effects and note that the benefits of spillover depend on specific technical levels, business models, and indexes related to specific industries (Duschl et al., 2015). Cities of different sizes have different forms of agglomeration effects; large cities have stronger urbanization economies, while small cities have stronger localization economies (Glaeser et al., 1992). Capital- and technology-intensive industries need technological support and capital requirements to offset high risks. Industry development in each link in the industry chain in large cities is complete. Firms can cooperate with scientific research institutions, financial institutions, public institutions, and consulting agencies in large cities to gain financial, technical and informational support (Fu & Hong, 2008). Furthermore, capital- and technology-intensive industries have complex industrial chains and require many intermediate products. Downstream capital- and technology-intensive industries benefit more from economies of scale in large cities’ intermediate product markets (Ke & Zhao, 2014; Krugman & Venables, 1995). However, labour-intensive industries are still at the low end of technology, and firms in specialized markets can obtain production knowledge simply by imitating each other. In addition, labour-intensive industries have a low need for intermediate goods, indicating that these industries are less dependent on the economies of scale of intermediate goods markets in large cities. Regarding firm characteristics, large firms have an advantage in seeking non-local intermediate suppliers, which reduces the demand for local suppliers (Porter, 1998). In addition, large-scale firms can provide better wages and attract more labour. Altogether, employment stability is high (Audretsch & Thurik, 2001), and the labour pool cannot exert its role. In addition, regions with large firms hinder knowledge spillovers and foster a business culture, which, in turn, hinders innovation (Chinitz, 1961; Saxenian, 1994; Thurik & Carree, 1999). Finally, larger firms have a higher degree of vertical integration, which prevents face-to-face communication (Enright, 1995) and hinders the formation of agglomeration effects. The survival period of firms could also affect the agglomeration effects. As the survival period of firms expands, firms can gain experience through “learning by doing” (Andersson & Lööf, 2011; Thompson, 2005), thereby reducing its dependence on the external environment, but firms with too long a lifespan may fall into a dilemma due to problems in the early part of their life, such as vague ownership, and therefore be more dependent on the external industry chain for survival. Regarding firm ownership, state-owned firms in China have a very important status for local governments, and thus, governments tend to protect the interests of state-owned firms and give them more preferential policies (Bai et al., 2004). Therefore, the incentive of state-owned firms to reduce transaction and production costs by linking with other firms is weak. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 394 | 395 Regarding regional characteristics, under the context of administrative decentralization and “promotion tournaments” (Li & Zhou, 2005), Chinese local governments adopt location preferences, such as tax benefits, interest-free or low-interest loans and public subsidies, including energy, raw material, land and technology subsidies, to promote urban economic development. Generally, cities higher in the administrative hierarchy can obtain more state resources, such as physical and infrastructural inputs and financial supports (Chan & Zhao, 2002; Zhang & Zhao, 2001), and thereby attract targeted firms to clusters (Haughwout et al., 2004; Koven & Lyons, 2002; Martin & Rogers, 1995). In cities, local governments also allocate resources through providing land, public services, infrastructure and subsidies to firms in economic development zones. The policy of attracting investment has led to the concentration of industries in the economic development zones of the cities (Howell, 2019; Koster et al., 2016; Lu et al., 2019). Local governments in cities with a higher administrative status and cities with special economic development zones can attract firms in all positions of the industrial chain through regionally targeted policies (Lu et al., 2019). Therefore, the industrial chain is more closed through overall planning, and firm productivity is promoted through forward and backward spillovers (Hu & Xie, 2014). The above research findings only emphasize the impact of agglomeration effects. However, there is heterogeneity among firms, and inefficient firms excluded from markets through competition could also improve the productivity of industrial agglomeration (Arimoto et al., 2014; Behrens et al., 2014; Combes et al., 2012; Syverson, 2004). If only the agglomeration effects are considered, the endogeneity problem between agglomeration and productivity could be severe (Ciccone, 2002; Henderson, 2003; Rosenthal & Strange, 2004). To address such endogeneity, several scholars use instrumental variables to address the endogeneity problem (Ciccone, 2002; Ciccone & Hall, 1996; Henderson, 2003). However, the effects of agglomeration on productivity may still be overestimated without considering selection effects (Baldwin & Okubo, 2006). Melitz and Ottaviano (2007) were the first to theoretically verify the existence of competitive effects. Combes et al. (2012) integrated these two effects into a framework and tested this framework using French manufacturing data. The empirical evidence shows that the differences in the productivity of French manufacturing firms are mainly derived from agglomeration effects and that selection effects do not exist. In China, Yu and Yang (2014) noted that the method used by Combes et al. (2012) has a high degree of non-linearity in optimizing the objective function and that the bootstrap method runs at a slower speed in calculating the parameters. These authors improved the regression method proposed by Combes et al. (2012) and used NLS based on a grid search method to reduce the degree of non-linearity in the optimization objective function and increase the running speed. The authors found that the productivity advantage of large cities in China is derived from agglomeration effects rather than selection effects and that an S-type relationship exists between city size and accumulated agglomeration effects. Based on the above analysis, we propose the following four research hypotheses to guide our empirical analysis. Hypothesis 1 Capital- and technology-intensive industries have a higher optimal city size than labour-intensive industries. Hypothesis 2 The agglomeration effects of smaller firms are stronger than those of larger firms. Hypothesis 3 State-owned firms benefit less from agglomeration than non-state-owned firms. Hypothesis 4 Cities with higher administrative levels and cities with special economic development zones have stronger agglomeration effects. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG 3 3.1 | | WANG T H E O R E T ICA L MO D E L A ND M ETHODOLOGY | Theoretical model Drawing upon the theoretical model proposed by Combes et al. (2012), it is assumed that there are I cities in a country and that the population of city i is Ni. The products of the consumer utility function include numeraire and differentiated products. The production of numeraire assumes a constant return to scale, while differentiated products are increasing returns to scale. According to first-order conditions, consumers’ demand functions for each differentiated product can be obtained. Moreover, the price at which a certain consumer’s demand for a differentiated product in city i is exactly zero is the cutoff price h−i , and products higher than the cutoff price will not be purchased. The demand function can be expressed as a production function with a critical price and product prices. Firms that produce a differentiated product need to pay s units sunk cost before entering the market, and only then will the labour demand per unit of product, h, be known. Assuming wage is one unit, h is the marginal cost of the firm. The draw of h is random, the probability density function is assumed to be g(h), and the cumulative distribution function is G(h). Since the marginal cost and price under monopolistic competition are equal, the threshold cost (cutoff) for any firm in a city to survive is also h.1 All firms above this value have negative profits and cannot survive. At equilibrium, supply equals demand, and the demand from city j to a firm in city i is the individual demand multiplied by city j’s size. In addition, the marginal cost of the firm is τijh, where τij is the iceberg cost of a unit of product transported from city i to city j (when i = j, τij = 1, and when i ≠ j, τij > 1). The production cost for the threshold of city j faced by a firm in city i is h−j โ๐ ij. Then, we can determine the function of the profit of a given firm in city i from city j with respect to price, namely, Πij = f(h−j , ๐ ij , h). Since firms are under monopolistic competition, entry and exit will end when the expected profits are zero. The expected operating profit of a certain firm in each city of city i is the expected value of its profit, where the probability density function of h is g(h); thus, the sum of the N expected profits in all cities and the sunk cost can be balanced. By combining N equations, the critical threshold cost of city j can be expressed as h−j = h(N1 , . . . , Nj , . . , ๐, . . . , s, g(h)). The effect of agglomeration effects stems from the interaction between labour forces (Fujita & Ogawa, 1982; Lucas & Rossi-Hansberg, 2002) under the assumption that the effective labour force −(ln(di −1) that a person in city i can provide . ∑ ∑ is ai h Among them, ai = f1 (Ni , ๐ฟ Nj ), di = g1 (Ni , ๐ฟ Nj ) ai ≥ 1, 1 ≤ di ≤ e (when all cities have a scale j≠i j≠i of 0, ai, di are both 1). The setting of δ is based on the interaction between cities, i.e., there will be spatial decay within the city, i.e.๐ฟ ∈ [0, 1]. In addition, h−(ln(di −1)) is set based on the difference in firm costs, i.e., the effective labour that a person can provide depends on city size and the production cost of the firm. Therefore, the number of labourers to be employed by a certain firm in city i is the product of the total output and the labour demand per unit of product divided by the unit effective labour that the workers in the firm can provide, which can be derived as follows: ∑ li (h) = Qij (h) × hโ[ai h−(lndi −1) ] j Firm productivity is defined as the total output of a firm divided by the labour force employed; ∑ โ Qij (h) โ โ j โ thus, the efficiency of a firm can be expressed as ๐i (h) = ln โ โ = Ai − Di ln(h). โ li (h) โ โ โ 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 396 | 397 Among them, Ai ≡ ln(ai ), Di ≡ ln(di ). In addition, all firms above the critical cost(of)city i will be − eliminated. Suppose Si is the share of a firm that is eventually eliminated Si ≡ 1 − G h Therefore, A, D and S depict the degree of transformations of firm productivity in large cities relative to those in small cities. If A > 0, firm productivity in large cities is shifted to the right relative to that in small cities, i.e., firms in large cities benefit more from agglomeration effects. D characterizes the extent of dilation of firm productivity distribution in large cities relative to that of firm productivity distribution in small cities. If D > 1, the firm productivity distribution in large cities is dilated relative to the firm productivity distribution in small cities. The difference between A and D is that the former will cause all firms in the same city to receive the same degree of benefit, while the latter is based on heterogeneous firm productivity. The degree of benefit due to the size of the city will change according to firm productivity. High-productivity firms benefit more. S characterizes the truncation degree of the firm productivity distribution in large cities relative to the firm productivity distribution in small cities. If S > 0, the distribution of firm productivity in large cities has a left truncation relative to that in small cities. ( ) ฬ Referring to the study by Combes et al. (2012), let F(๐) = 1 − G e−๐ be the potential cumulative distribution of the density function of logarithmic firm productivity in the absence of agglomeration and selection effects. The agglomeration effects cause a right shift and dilation of the distribution, while selection effects imply left truncation. Therefore, the actual firm productivity distribution is obtained by transforming the potential logarithmic firm productivity distribution. It can be proven that the cumulative distribution function Fi (Φ) of the logarithmic firm productivity in city i is given as follows: โง ฬ โช F Fi (๐) = max โจ0, โช โฉ ๏ฟฝ ๐−Ai Di ๏ฟฝ โซ − Si โช โฌ 1 − Si โช โญ (1) As the cumulative distribution form of the logarithmic firm productivity is unknown, it is not feasible to directly obtain the parameters of different cities. Therefore, Combes et al. (2012) believe that the relative parameters of cities can be estimated by comparing the cumulative distribution functions of the logarithmic firm productivity in different cities. Therefore, the cumulative distribution function Fj (Φ) of the logarithmic firm productivity of a similar city j can be expressed as follows2: โง Fฬ โช Fj (๐) = max โจ0, โช โฉ ๏ฟฝ ๐−A ๏ฟฝ j − Sj โซ โช โฌ 1 − Sj โช โญ Dj (2) Let A = Ai–DAj, D = Di/Dj, and S = (Si–Sj)/(1–Sj). Assume city i is larger than city j. According to the above description, it can be known that A, D, and S are the relative positions and left truncation of the cumulative distribution function of the logarithmic firm productivity between cities. If agglomeration effects and selection effects can promote firm TFP, A > 0, D > 1, and S > 0. When Si > Sj, ๏ฟฝ ๏ฟฝ โง โซ ๐−A โช Fj D − S โช Fj (๐) = max โจ0, โฌ 1−S (3) โช โช โฉ โญ 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG When Si < Sj, Fj (๐) = max { 0, Fi (D๐ + A) − S } (4) −S 1 − 1−S To obtain the parameter estimation formula, the cumulative distribution function of the logarithmic firm productivity is converted into a moment estimation represented by quantiles. First, we transform (3) and (4) as follows: assume that the potential cumulative distribution function Fฬ is invertible; then, Fi and Fj are also invertible. Let ๐i (u) = F−1 be the quantile of Fi at probability i (u) −1 u and ๐j (u) = Fj (u) indicate the quantile of Fi at probability u. Through transformation, we obtain the following: m๐ (u) = ๐i (rs (u)) − D๐j (S + (1 − S)rs (u)) − A = 0, u ∈ [0, 1] (5) ) rฬs (u) − S A + = 0, u ∈ [0, 1] 1−S D (6) m ฬ ๐ (u) ≡ ๐j (ฬrs (u)) − 1 ๐ D i ( } ( { }) { S S + 1 − max 0, − 1−S u, rฬs (u) = max {0, S} + (1 − max {0, S}) u. where rs (u) = max 0, − 1−S Combes et al. (2012) used the quantile approach to estimate the above model. Combes et al. (2012)’s method is an extension of the generalized method of moments (GMM) method, which uses continuous moments to estimate parameters under an infinite set. To estimate the parameters of (5) and (6), Combes et al. (2012) transformed the moment condition of the theoretical quantile into the moment condition of the sample quantile; thus, the sample estimation of λi and λj must be determined first. Using city i as an example, first, the logarithmic firm productivity is listed in ascending order. Assuming that the value of firm productivity is f, let ( ) ( ) { } Φi = {๐i (0) , …, ๐i fi and ๐i (0) < … < ๐i (f); then, the quantile is ๐ฬ i k = ๐i (k) , ∀k ∈ 0, …, fi , u ∈ (0, 1). fi The sample quantile estimation can be expressed as follows: ฬ ๐i ๐i (u) = (k∗i + 1 − uEi )ฬ ( k∗i Ei ) + (uEi − k∗i )ฬ ๐i ( k∗i + 1 Ei ) (7) where k∗i = int (uEi). For city j, the index of (7) is replaced with j. Then, Combes et al. (2012) estimated the parameter samples for solutions (5) and (6) by minimizing the following objective function: ฬ ๐ = argmin M(๐) (8) 1 1 ฬฬ ๐ (u))2 du where M(๐) = ∫ 0 (ฬ m๐ (u))2 du + ∫ 0 ( m ∑ ∑ 1 1 K Among them, ∫ m ฬฬ ๐ (u))2 du ≈ 1 Kk= 1 ( m ฬฬ ๐ (uk )2 +. m๐ (uk )2 + m ฬ ๐ (uk−1 )2 )(uk − uk−1 ), ∫0 ( m ฬ ๐ (u)2 du ≈ 21 k = 1 (ฬ 0 2 ฬฬ ๐ (uk−1 )2 )(uk − uk−1 ) m 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 398 3.2 | | 399 Introduction to the NLS method based on a grid search However, Yu and Yang (2014) noted that although the method approximates the number of quantile rows linearly, the solution for obtaining parameters A, D, and S is still a very complicated and highly non-linear function, rendering the solution process very complex. Therefore, this paper adopts the non-linear least squares (NLS) method proposed by Yu and Yang (2014) to estimate the regression results. This method is applicable when the explanatory variable and dependent variable are non-linear. A typical non-linear regression model is listed as follows: yt = xt (๐ฝ) + ut yt is the explanatory variable, and β is the estimated parameter with k dimensions. Xt(β) is a non-linear regression function. Xt(β) indicates that the regression function will change with the observed value mainly because Xt(β) depends on the explanatory variable. NLS is widely used in the theory of industrial agglomeration. For example, some scholars use the NLS method to estimate the exponential function to observe the spatial decay of agglomeration effects based on the geographic distance (Ahlfeldt and Feddersen, 2018; Amiti and Cameron, 2007; Andersson et al., 2004; Rice et al., 2006), and some scholars use NLS estimation models to measure agglomeration and crowding effects (Ahlfeldt & Feddersen, 2018; Ciccone & Hall, 1996). The dependant variable and explanatory variables in the function in this paper also have a non-linear relationship; thus, the NLS method can be used for the regression estimation. The objective function of NLS is as follows: Q(๐ฝ) = SSR(๐ฝ) = n ∑ (yt − xt (๐ฝ))2 = (y − x(๐ฝ))T (y − x(๐ฝ)) t=1 The key to NLS estimation is to find the β value that minimizes SSR(β). Many algorithms can be used to minimize the smooth function Q(β). Most algorithms operate basically the same. The algorithm processes a series of iteration steps. In each iteration step, the algorithm starts with a specific β and attempts to find a better estimation. The algorithm first selects the direction for the search and then decides how far to proceed in that direction. After completing the operation, the algorithm determines whether the current value of β is close enough to the local minimum value of Q(β). If it is, the algorithm stops. Otherwise, the algorithm will choose another search direction and repeat the process. The most common method used to estimate NLS is the Newton-Raphson method. The following part provides a simple introduction to the Newton-Raphson method. Assuming that Q(β) is twice continuously differentiable, given the initial value of β(0), the second-order Taylor expansion formula that is subsequently used is expanded around β(0) to obtain the approximate value of Q(β) to Q*(β) as follows: 1 Q∗ (๐ฝ) = Q(๐ฝ (0) ) + gT(0) (๐ฝ − ๐ฝ (0) ) + (๐ฝ − ๐ฝ (0) )T H(0) (๐ฝ − ๐ฝ (0) ) 2 (9) ๐g where g(๐ฝ) = ๐๐ฝ is the gradient of Q(β), which is the column vector with dimension k, and H(β) is 2 the Hessian matrix of Q(β), which contains the elements ๐๐๐ฝQ(๐ฝ) , a matrix of order k×k. To simplify the i ๐๐ฝ j notation, g(0) and H(0) represent g(β(0)) and H(β(0)), respectively. It can be easily observed that the first-order condition for a minimum of Q*(β) with respect to β can be written as follows: 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG g(0) + H(0) (๐ฝ − ๐ฝ (0) ) = 0 Solving these equations will produce a new value of β, which we call β(1), as follows: (10) ๐ฝ (1) = ๐ฝ (0) − H−1 g (0) (0) Equation (10) is the core of Newton-Raphson. If the quadratic approximation Q*(β) is a strictly convex function, β(1) is the global minimum of Q*(β) if and only if the Hessian matrix H(0) is positive definite. In addition, if Q*(β) is a good approximation of Q(β), β(1) should be close to ฬ ๐ฝ , and Q*(β) is the minimum value of Q(β). The Newton-Raphson method involves repeatedly using Equation (10) to find a series of values (β(1), β(2)…). When the original function Q(β) is a quadratic function that has a global minimum at ฬ ๐ฝ , the Newton-Raphson method will obviously find ฬ ๐ฝ in the first step because the quadratic approximation is then exact. When Q(β) is approximately quadratic, because all square sum functions are close enough to their minimum values, the Newton method usually converges quickly. Consequently, based on NLS, Yu and Yang (2014) proposed a simplified solution to estimate (8). k ∈ [1, …, K], uk–uk–1 = b, where b is a fixed constant; thus, the objective function M(θ) of (8) can be written as follows: (11) N(๐) = N1 (๐) + N2 (๐) Among them, √ ∑K ∑K 2 , a = 1, k ∈ [2, …, K], a = a = 1โ 2. ฬ N1 (๐) = k = 1 (ak m ฬ ๐ (uk ))2 , N2 (๐) = (a (u )) m ฬ k( k ( (k = )) ( )) 1 ( ( )) 1 k ๐ k y1k (S) = ak ฬ ๐i rs uk , x1k (S) = ak ฬ ๐j S + (1 − S) rs uk , y2k (S) = ak ฬ ๐j %ฬrs uk , Let ( ( ) ) . x2k (S) = (ak ฬ ๐)i rฬs uk − S))โ (1(− S) ) ฬ can be expanded into a linear function as ak m ฬ ๐ uk ( and a m ฬ u k ๐ k ) ( ) ฬฬ ๐ uk = y2k (S) − D−1 x2k (S) − D−1 Aak follows:ak m ฬ ๐ uk = y1k (S) − Dx1k (S) − Aak , ak m We define the following: โก y11 (S) โค โข โฅ Y1 (S) = โข โฎ โฅ , โข y (S) โฅ โฃ 1k โฆ โก x11 (S) โค โข โฅ X1 (S) = โข โฎ โฅ , โข x (S) โฅ โฃ 1K โฆ โก y21 (S) โค โข โฅ Y2 (S) = โข โฎ โฅ , โข y (S) โฅ โฃ 2k โฆ โก x21 (S) โค โข โฅ X2 (S) = โข โฎ โฅ โข x (S) โฅ โฃ 2K โฆ The functions N1 (θ) and N2 (θ) can be converted as follows: N1 (๐) = [Y1 (S) − DX1 (S) − Aa]๏ฟฝ [Y1 (S) − DX1 (S) − Aa] [ ] [ ] 1 A ๏ฟฝ 1 A N2 (๐) = Y2 (S) − X2 (S) + a Y2 (S) − X2 (S) + a D D D D ( ) Among them, a๏ฟฝ = a1 , โฏ, aK . [ ] [ ] [ ] [ ] [ ] Y1 (s) X1 (s) 0k a 0 We also define Y (S) = , Z1 (S) = , Z2 (S) = , d1 = , d2 = k . 0k X2 (s) a Y2 (s) 0k Then, (11) can be equivalently transformed as follows: 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 400 | 401 โง โซ N(๐) = ๐(S)๏ฟฝ ๐(S) โช โช 1 A โฌ โจ Where ๐(S) = Y(S) − DZ (S) − (S) − Ad + Z d 1 1 โช D 2 D 2โช โฉ โญ When S is a constant, (8) can be simplified to solve the non-linear LS estimation. Subsequently, the Newton-Raphson iteration can be used to determine the parameter value.However, in this paper, it may be difficult to converge by directly using the Newton-Raphson method to iteratively solve the problem. Therefore, it is possible to use a grid search to determine the specific values of a certain parameter and then use the Newton-Raphson method to perform the NLS estimation. A grid search is a type of optimal algorithm. In the process of searching, the interval of the parameter is set first, and then, the step is set. When the step is large, the accuracy is low. When the step is small, the accuracy is high. If the search interval of X is [Xmin, Xmax], SX = (Xmax–Xmin)/KX is the step. For X, the Kth search value is Xmin+(k–1)*SX, 0 ≤ k ≤ KX. In this paper, the interval is divided into Q equal divisions with a certain accuracy in a given search interval [c, d]. The parameter S uses the grid search method to divide any discontinuous points by the above interval to calculate Y (S), Z1 (S), and Z2 (S) and uses the NLS estimation to solve parameters A and D as follows: Y(S) = DZ1 (S) + A 1 Z (S) + Ad1 − d2 + ๐(S) D 2 D Then, the corresponding parameter S and non-linear estimation are determined according to the corresponding minimum mean squared residual (MSR). Here, we define c = −0.5, d = 0.5, and Q = 100. Furthermore, to ensure the robustness of the search results, we only use the moment conditions in (5) and discard those in (6) to re-estimate the parameter when constructing the optimization objective function. The objective function is simplified to N1 (θ). Meanwhile, the function is simplified to the linear form of A and D, and the parameter value can be obtained by using the LS estimation. The corresponding linear equation is as follows: Y1 (S) = DX1 (S) + Aa + ๐1 (S), where ε1 (s) is the corresponding error term. 4 4.1 | DATA S OU RC E A N D VA R IABLES | Data source The data used in this article are derived from annual surveys of industrial firms from 1998 to 2007. The data are collected by corresponding regions and departments, which annually submit the data to the State Statistical Bureau of China according to the country’s statistical scope, calculation methods, statistical calibration, and reporting catalogues. The greatest feature of China’s industrial firm database is that it has many statistical indicators and a complete statistical scope. The statistical scope of the Chinese industrial firm database contains large and above medium-sized manufacturing firms in the region of mainland China, including state-owned firms, collectively run firms, stock-cooperation ventures, joint ventures, limited liability firms, limited firms, private firms, other domestic firms, Hong Kong firms, Macao- and Taiwan-invested firms, and foreign-invested firms. The industrial 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG statistical indicators include the industrial added value, total industrial output value, industrial sales, other indicators, financial cost indicators and employees’ wage. The codes of the administrative divisions reported by the industrial firm database greatly vary across different years. For the sake of comparison convenience, this article uses the administrative division code issued by the National Bureau of Statistics on December 31, 2002 as the standard. According to the national administrative division adjustment document announcement, we merge, replace, delete or add the code of the administrative divisions of all years to unify the data to the standard in 2002. In addition, since China’s national economy industry classification system was revised in 2002, the data classification of China’s industrial firms in 1999–2002 use the national economy industry classification system GB/T4754-1994. To unify the industry calibration and allow the data to be easily processed, this article adjusts the industry code from 1999 to 2002 according to the National Economic Industry Classification GB/T4754-2002. Finally, it is inevitable that some flaws appear during the survey and that some missing or unreasonable values of variables exist (such as negative output) that are generated during actual production and operation; thus, we also exclude some samples. In addition, this article excludes firms whose operations have been discontinued, firms under construction, firms that have been cancelled, firms under bankruptcy, and firms in other non-operational states and only uses data with an operating status code equal to 1. Finally, this article uses the method proposed by Xie et al. (2008) and excludes samples with fewer than 8 employees or samples in which the ratio of the added value to sale is less than 0 or greater than 1. 4.2 | City size We use the population of prefecture-level cities to measure city size. The data are derived from the China Urban Statistical Yearbook. Due to the lack of data of some city indicators, only 213 of the 283 cities above the prefecture level remain after deleting the samples with missing values. 4.3 | Firm productivity We use the total factor productivity (TFP) to measure a firm’s productivity. When measuring a firm’s TFP, simultaneity bias, selectivity and attrition bias exist. The former implies that a firm can partially perceive its productivity information and change the factor input level to maximize profits, resulting in endogeneity in the input factors; the latter occurs because the factor input of a firm determines its survival probability in the face of exogenous shocks, biasing the capital estimation. This paper uses the semi-parametric estimation method (referred to as the OP method) proposed by Olley and Pakes (1996) to estimate firm TFP.3 This method makes investment decisions based on the current productivity of firms and uses the current investment of firms as an agent variable representing unobservable firm productivity shocks to resolve the simultaneity bias. Figures 1 and 2 show the geographical distribution of the city sizes and the corresponding average TFP of the firms. To a certain extent, the colour depth of the two variables in the figure shows a corresponding relationship. Figure 3 shows the probability density distribution of the logarithmic TFP of firms above the median city size and firms below the median city size. It can be found that overall, the productivity probability density distribution function of urban firms above the median city size is generally shifted farther to the right than that of urban firms below the median size. Specifically, the average TFP of urban firms above the median city size is 3.56, and the average TFP of urban firms below the median city size is 3.46. Subsequently, this article divides the industries 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 402 FIGURE 1 | 403 Distribution of the mean urban population into labour-intensive industries and capital- and technology-intensive industries and further characterizes the probability density distribution function of the logarithmic TFP of firms above and below the median city size (see Figures 4 and 5). The average TFP of the capital- and technology-intensive industries is 3.594 among those above the median city size and 3.496 among those below the median city size. The average TFP of labour-intensive industries is 3.536 in cities above the median size and 3.411 in cities below the median size. In addition, this article describes the probability density distribution of firms with different ownership (Figures 6 and 7) as follows: the average TFP of non-state-owned firms in cities above the median size is 3.656, while the average TFP in cities below the median is 3.573; the average TFP of state-owned firms in cities above the median city size is 2.563, while the average TFP of firms in cities below the median is 2.381. This article also characterizes the probability density distributions of firms above and below the average firm size (Figures 8 and 9). When classifying the sample according to the average firm size, we find the following: the average TFP of below-average sized firms in cities above the median city size is 3.605, the average TFP of below-average sized firms in cities below the median is 3.541, the average TFP of above-average sized firms in cities above the median city size is 3.628, and the average TFP of above-average sized in cities below the median is 3.545. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG FIGURE 2 5 5.1 | Distribution of the mean logarithmic total factor productivity M A IN R E S U LTS | Basic regression The main results obtained using the NLS estimation based on a grid search are presented in Table 1. The results reflect 28 two-digit level manufacturing industries and all industries together using the OP method. Columns (1)-(5) in Table 1 include the estimation of A, D, and S, the corresponding standard error and the regression’s R2. In Column (2), we can observe that D is larger than 1 in 18 of the 28 sectors and in the all-sector estimation. This finding shows that more than half of high-productivity firms benefit more from being located in large cities. In addition, the estimated value of industry D in all industries is 0.976, showing that the heterogeneity of the agglomeration effects is not significant in the all-sector estimation. Using industries with industry code 18 (textile, clothing, shoe, and hat industries) as an example, if the logarithmic TFP distribution in an area below the city size average is shifted by 0.062, the firms will have a 9.63%, 10.1%, and 10.6% productivity advantage in the median, second quartile and third quartile of the distribution, respectively. In Column (4), the estimated values of A in 18 of the 28 sectors are significantly larger than zero, indicating that firms benefit more in larger cities because of agglomeration effects. This result is consistent with the theory proposed by 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 404 | 405 F I G U R E 3 Probability density distribution of the logarithmic total factor productivity of all industries in cities above (solid) versus below (dashed) the median city size F I G U R E 4 Probability density distribution of the logarithmic total factor productivity of labor-intensive industries in cities above (solid) versus below (dashed) the median city size Krugman (1991). In addition, if all industries are considered, the parameter of A is 0.821. This finding shows that the average productivity of firms in large cities is e ^ 0.821-1 or 127% higher than that of firms in small cities due to agglomeration effects. However, we find that regardless of whether we examine the whole sample or one sector, S remains zero or near zero, indicating that no selection effects 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG F I G U R E 5 Probability density distribution of the logarithmic total factor productivity of capital technology intensive industries in cities above (solid) versus below (dashed) the median city size F I G U R E 6 Probability density distribution of the logarithmic total factor productivity of the non-state-owned firm sample in cities above (solid) versus below (dashed) the median city size exist in large cities in China, confirming the results reported by Combes et al. (2012). Column (6) reports the R2 of the productivity distribution based on a grid search. The R2 of 15 of the 28 industries are above 0.8. However, in some industries, the estimated value of A is negative, indicating that these industries experience a congestion effect. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 406 | 407 F I G U R E 7 Probability density distribution of the logarithmic total factor productivity of the state-owned firm sample in cities above (solid) versus below (dashed) the median city size F I G U R E 8 Probability density distribution of the logarithmic total factor productivity of the below averagesized firms in cities above (solid) versus below (dashed) the median city size 5.2 | Sensitivity analysis and robustness checks To ensure the accuracy of the highest quality search and avoid possible local solutions for the nonlinear model optimization, we use LS estimation based on partial moments to calculate the parameters in a grid search framework (see Table 1). It can be observed that the optimal solutions of the two 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG F I G U R E 9 Probability density distribution of the logarithmic total factor productivity of the above averagesized firms in cities above (solid) versus below (dashed) the median city size search methods are close, but the value of A estimated by LS is slightly larger than that estimated by NLS, while the estimated value of D is smaller. Using industries with code 13 as an example, the A and D estimations are 0.322 and 0.936, respectively, under the NLS estimation and 0.329 and 0.934, respectively, under the LS estimation. Figure 10 reports the mean square residuals in which the overall data are used to estimate the grid search under two moment conditions. It can be found that S = 0 is the only minimum solution of the MSR. To eliminate the bias caused by the OP method when estimating firm TFP, this article uses ordinary least squares (OLS), fixed-effect, and LP methods (Levinsohn et al., 2003) to re-estimate the TFP of the overall sample (see Table 2). The parameters A, D and S estimated by the three methods are basically similar to those estimated by the previous OP method. Because some determinants of production are unobserved by econometricians but are observed by the firm, when using the OLS method, an endogeneity problem exists. The fixed-effect model can only solve endogeneity problems related to a time-invariant shock, which usually underestimates the coefficient of capital (Griliches & Mairesse, 1995). The OP and LP method allow the optimal input decision to be converted into “observed” unobserved productivity shocks. Levinsohn et al. (2003) use a similar method but insert an intermediate input demand function instead of an investment function to control for unobserved productivity shocks. The OP method requires data with zero investment to be discarded, while Levinsohn et al. (2003) note that such data could sometimes account for a significant portion of the data. From the result, we can find the OP method estimator A = 0.227 is the closest to the LP method estimator A = 0.225 among 3 methods. The OLS method estimator D = 0.968 is the closest to LP method estimator D = 0.965 among 3 methods. S = 0 is still not significant in these three estimations. In general, the estimated value of A under the fixed-effect model is the largest, followed by that estimated using the OP method and finally that estimated by the OLS method. Some evidence shows that spatial externalities will decrease as the distance increases (Békés & Harasztosi, 2018; Briant et al., 2010). Fotheringham and Wong (1991) note that the MAUP renders multivariate analysis results no longer stable. Rosenthal and Strange (2001) also note that the influence 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 408 0 0 0 0.01 0 0 0.01 0 0.01 0 0 0 0 0 0 0.01 0 0 0 0 0 0 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 1.048 1.015 0.999 1.014 0.913 0.999 1.073 1.017 1.002 1.069 1.038 0.942 0.954 1.064 1.016 1.08 1.01 1.034 0.999 0.953 0.928 0.936 D 0.001 0.001 0.002 0.002 0.001 0.001 0.002 0.001 0.001 0.002 0.002 0.001 0.001 0.002 0.001 0.002 0.001 0.001 0.002 0.001 0.001 0.001 V(D) 0.095 0.346 0.433 0.322 −0.145 −0.059 0.014 0.06 0.4 0.08 −0.088 0.086 0.067 −0.219 −0.064 0.322 0.232 −0.205 0.033 −0.074 0.062 −0.002 A 0.004 0.003 0.008 0.006 0.005 0.004 0.006 0.003 0.003 0.006 0.007 0.005 0.004 0.006 0.004 0.008 0.003 0.004 0.01 0.005 0.003 0.005 V(A) 0.569 0.138 0.012 0.696 0.805 0.761 0.928 0.915 0.776 0.525 0.506 0.822 0.784 0.811 0.828 0.905 0.885 0.866 0.551 0.873 0.94 0.759 R 0 0 0 0 0 0 0.01 0 0 0 0 0 0 0.01 0 0.01 0 0 0.01 0 0 0 1.047 1.015 0.995 1.012 0.91 0.998 1.071 1.016 1.001 1.067 1.034 0.94 0.953 1.061 1.015 1.076 1.009 1.032 0.994 0.951 0.927 0.934 D 0.002 0.001 0.003 0.002 0.002 0.002 0.002 0.001 0.001 0.002 0.003 0.002 0.002 0.002 0.001 0.003 0.001 0.002 0.003 0.002 0.001 0.002 V(D) (9) 0.065 0.002 0.117 0.353 0.436 0.329 −0.141 −0.056 0.031 0.068 0.408 0.084 −0.08 0.089 0.069 −0.211 −0.052 0.33 0.236 −0.196 0.036 −0.057 A (10) S S (8) (7) (5) 2 (4) (6) (3) (1) (2) LS with partial moment condition NLS with all moment condition Basic regression results 0.006 0.005 0.012 0.008 0.007 0.005 0.008 0.005 0.005 0.009 0.01 0.007 0.005 0.009 0.005 0.012 0.005 0.006 0.014 0.007 0.005 0.007 V(A) (11) | (Continues) 65,291 23,530 31,196 108,273 61,493 15,742 6,493 25,303 96,637 10,067 17,180 27,972 36,097 15,243 22,590 30,213 66,339 111,731 1,779 20,744 29,601 73,386 Observations (12) 409 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Industry code TABLE 1 WANG 0 0 0 0 0 0 36 37 39 40 41 All sectors 0.967 1.077 1.062 1 1.002 1.015 1.031 0.002 0.001 0.001 0.001 0.001 0.001 0.001 V(D) 0.034 0.091 0.113 0.045 0.217 −0.125 −0.06 A 0.005 0.003 0.005 0.004 0.005 0.004 0.005 V(A) 0.708 0.953 0.907 0.301 0.671 0.888 0.885 0 0 0 0 0 0 0 0.965 1.076 1.061 0.998 1 1.013 1.029 D 0.002 0.001 0.002 0.002 0.002 0.002 0.002 V(D) 0.038 0.097 0.118 0.051 0.225 −0.122 −0.055 A (10) 0.008 0.005 0.007 0.006 0.007 0.006 0.007 V(A) (11) 1,229,359 13,790 39,106 80,685 64,644 54,099 102,053 Observations (12) WANG 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License Notes: A and D are the right shift and dilation degree of the potential cumulative distribution function of firm total factor productivity caused by agglomeration effects, and S is the probability that an inefficient firm is excluded from the cities. V(D) and V(A) are standard errors of parameter D and A. 0 35 D (9) S S (8) R2 (5) (7) (4) (6) (3) (1) (2) LS with partial moment condition NLS with all moment condition (Continued) | Industry code TABLE 1 410 FIGURE 10 | 411 Mean square residuals (MSR) of the grid search of knowledge spillover has boundaries. To test whether the agglomeration effects are spatially stable, this article uses programming to obtain the coordinates of the Baidu application programming interface (API) source based on the firm name and firm address and then uses ArcGIS to divide the area into equal area squares. The specific steps are as follows. First, we use the Baidu Maps API to obtain latitude and longitude information. Second, due to China’s policy restrictions, all domestic network map service providers encrypt and shift map data. Thus, data from a map server cannot be directly used for spatial analyses and require re-encoding into the international universal coordinate system WGS1984. Third, we use ArcGIS analysis tools to divide the space into 100 km × 100 km, 200 km × 200 km, and 400 km × 400 km squares (see Figures 11–13). Finally, based on the space boundaries of the squares, the number of the firms in different squares is separately summed4. The results are shown in Table 2. Although the values of the A estimators increase, which may be caused by the change in the city size measurement, the direction of the estimators coincides with the previous results. It is found that the results are still robust. 5.3 | Heterogenous agglomeration effects To further explore the heterogeneity of agglomeration effects in different industries, we divide the industries into capital- and technology-intensive and labour-intensive industries, separate the firm logarithmic TFP based on the city size into 19 groups in ascending order, and then use NLS based on a grid search to determine the parameter estimation of each neighbouring group, including group 2-group 1, group 3-group 2, and group 4-group 3, etc. It can be found that in the 19 groups, the estimated values of A in 10 groups of capital- and technology-intensive industries are significantly greater than 0 and those of D in 10 groups are greater than 1; the estimated values of A in 10 labour-intensive industries are greater than 0 and those of D in 9 groups are greater than 1. In addition, this article describes the trend in the cumulative value of parameter A, which depicts the change in the agglomeration effects (see Figure 14). It can be found that as the size of the city increases, the cumulative agglomeration 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | TABLE 2 WANG Robustness test S D V(D) A V(i) R2 Observations 0.002 0.213 0.005 0.702 1,147,993 Replacing the TFP measurement method Tfp_OLS 0 0.968 Tfp_Fe 0 0.971 0.001 0.228 0.005 0.773 1,147,993 Tfp_LP 0 0.970 0.001 0.227 0.004 0.791 1,147,993 Re-estimation based on spatial scale adjustment 100 × 100 0 0.782 0.002 0.930 0.007 0.877 1,016,434 200 × 200 0 0.807 0.002 0.856 0.007 0.875 1,020,056 400 × 400 0 0.785 0.002 0.931 0.007 0.879 1,020,056 Regression results of different ownership firms Sample of stateowned firms 0 1.005 0.001 0.065 0.004 0.806 113,349 Sample of nonstate-owned firms 0 0.962 0.001 0.276 0.002 0.936 1,116,425 Regression results under different administrative interventions Provincial city sample 0 0.937 0.001 0.359 0.004 0.898 130,259 Sub-provincial city sample 0 0.96 0.001 0.277 0.002 0.935 218,163 General city sample 0 0.995 0.001 0.146 0.004 0.859 926,368 Sample of Special Economic Zone Cities 0 0.893 0.001 0.553 0.004 0.931 38,525 Sample of non-special economic zone cities 0 0.978 0.002 0.192 0.006 0.699 1,141,881 Notes: A and D are the right shift and dilation degree of the potential cumulative distribution function of firm total factor productivity caused by agglomeration effect, and S is the probability that an inefficient firm is excluded from the cities. V(D) and V(A) are standard errors of parameter D and A. effects first increase and then decrease. The turning point of the inverted U-shaped curve of capitaland technology-intensive industries is even farther to the right than that of the labour-intensive industries. Capital- and technology-intensive industries experience the largest cumulative agglomeration effect in groups 18-17, while the average city size in this group is 12 million. Labour-intensive industries achieve the largest cumulative agglomeration effect in groups 8-7, while the average city size is 4.8 million. This finding shows that capital- and technology-intensive industries generate the strongest agglomeration effects in mega cities, while labour-intensive industries can achieve the strongest agglomeration effects in large cities.5 This conclusion coincides with hypothesis 1. Subsequently, to test the heterogeneity of the agglomeration effects in firms of different sizes, this article measures the size of the firm based on the average number of employees, arranges the average number of employees in the firm in ascending order, separate all firms into 18 groups, and estimates 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 412 FIGURE 11 100 km × 100 km FIGURE 12 200 km × 200 km | 413 parameters A, D, and S of the different groups. Then, we draw the trending figure of the agglomeration effects based on the estimated value of parameter A (see Figure 15). It can be found that the agglomeration effects show an inverted U-shape, i.e., medium-sized firms benefit the most from agglomeration effects, which is consistent with hypothesis 2. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | FIGURE 13 WANG 400 km × 400 km FIGURE 14 The relationship between the city size and cumulative agglomeration effects (A) in capital technology-intensive industries (solid line) and labour-intensive industries (dashed line) To examine whether there is a difference in the agglomeration effects of firms based on their survival time, this paper groups firms according to the firm age. To exclude outliers, this article removes firms aged over 200 years or less than 0 years and then groups the remaining firms in ascending order to examine the agglomeration effects and selection effects within different groups. As the age group 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 414 FIGURE 15 | 415 The relationship between the firm size and agglomeration effects (A) increases, the value of A decreases from 0.139 at the beginning to −0.056 in group 7 and then rises to 0.229 in group 18, indicating that the agglomeration effects show a U-shaped trend (see Figure 16). This finding shows that as firms grow older, agglomeration effects initially weaken but later increase. This paper also estimates the sample by dividing the firms into state-owned firms and non-stateowned firms (see Table 2). It can be found that the agglomeration effects experienced by state-owned firms are significantly smaller than those experienced by non-state-owned firms, which is consistent with hypothesis 3. To test whether administrative intervention could influence the agglomeration effects, we divided all cities into provincial cities, vice-provincial cities, and common cities to test whether the agglomeration effects vary among cities at different administrative hierarchical levels. As a result, we find that as the administrative hierarchy decreases, the estimated value of A continues to decline (see Table 2). The estimated value of A in provincial cities is 0.359, while that in common cities is only 0.146, indicating that being higher in the administrative hierarchy does cause stronger agglomeration effects. In addition, we conduct a regression after classifying the cities according to whether they have special economic zones (SEZs). We can find that the agglomeration effects of cities with SEZs are significantly higher than those of cities without special economic zones as follows: the parameter A of the former is 0.553, which is almost double the parameter A of the latter, i.e., 0.192 (see Table 2). These findings are consistent with hypothesis 4. 5.4 | Why are selection effects not significant? An explanation from the perspective of zombie firms In this section, we further examine why the selection effects are not significant6 in China. The promotion of local officials in China is closely linked to the economic development of their jurisdiction (Li & Zhou, 2005), and the bankruptcy of firms has a significant effect on the local GDP and employment rates (Min & Qun, 2012). To stabilize the economy, local officials may give higher subsidies to firms with lower productivity or those that are “in the red”. In addition, to avoid defaults on bad loans (Hoshi, 2006; Peek & Rosengren, 2005), banks continue to provide loans to these firms, preventing 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | FIGURE 16 WANG The relationship between firm age and agglomeration effects (A) inefficient firms from elimination (McGowan et al., 2017); these firms saved from elimination due to government support are often called “zombie firms” (Caballero et al., 2008). Although zombie firms do not produce benefits, the government invests production resources in these firms (Tan et al., 2016), leading to a significant increase in their survival rate, a distortion in competition (Nishimura et al., 2005) and chaotic market competition (Caballero et al., 2008). Therefore, we use a semi-parametric Cox survival model to analyse the impact of government intervention on the survival risk of zombie firms and the reasons for the non-significant selection effects. We use the actual profit method used by He and Zhu (2016) to identify zombie firms. We use the administrative hierarchy of the city(Rank) and economic development zone index(Zone_index) to measure the resources in a city. We divide all cities into provincial cities, vice-provincial cities, and common cities as follows: 2 represents provincial cities, 1 represents vice-provincial cities, and 0 represents common cities. The construction of the economic development zone index is described in Démurger et al. (2002). By referring to the previous literature concerning the survival probability of firms and zombie firms (Agarwal & Gort, 1996; Dimara et al., 2008; Doi, 1999; Du & Li, 2019; Evans, 1987; He & Yang, 2015; Jovanovic, 1982; Mata & Portugal, 1994; Olley & Pakes, 1996; Shen & Chen, 2017), we also input the logarithmic firm scale (LnScale), capital density (Capitaldensity), industry concentration (HHI), whether to export (Export_dummy), firm age (Firm_age), industry dummy variables (Industry_dummy), province dummy variable (Province_dummy), and a time dummy (Year_dummy) as control variables in the Cox survival model. The regression coefficients of the Rank and Zone_index are significantly negative at the 1% level, indicating that firms in cities higher in the administrative hierarchy and those with a higher economic development zone index have a higher probability of survival. This finding confirms that resources increase the survival of zombie firms. Subsequently, this article divides the sample into state-owned firms, foreign-owned firms and private firms. The results are basically robust. The improvement in firm productivity originates from a transfer of resources from inefficient to efficient firms (Duranton et al., 2014). Foster et al. (2006) use data of the US service industry and find that the productivity of exiting firms is much lower than that of existing firms, but the productivity of new firms is higher than that of mature firms. In fact, the existing “zombie firms” in China occupy the production factors invested by the government, significantly impeding patent applications and the TFP of normal firms (Tan et al., 2016). Over time, this development model is not conducive to the upgrading of industrial clusters. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 416 6 | | 417 CO NC LUSION S Past studies have analysed the influence of agglomeration on productivity. However, few existing studies have comprehensively evaluated the heterogeneity of agglomeration effects while considering selection effects. Therefore, this article uses data of Chinese industrial firms from 1998 to 2007 and finds that the agglomeration effect is an important mechanism for improving firm TFP. However, agglomeration effects are quite different across firms in different industries or of different ages, sizes or ownership or in regions with different amounts of resources. By grouping the firms into capital- and technology-intensive industries and labour-intensive industries, we find that the optimal agglomeration scale for capital- and technology-intensive industries is larger than that of labour-intensive industries. We also find that the firm size and cumulative agglomeration effects have an inverted U-shaped relationship, while a U-shaped relationship exists between firm age and agglomeration effects. State-owned firms experience weaker agglomeration effects than non-state-owned firms. In addition, the agglomeration effects are greater in cities higher in the administrative hierarchy and those with special economic zones. Furthermore, we use a Cox survival analysis to analyse the influence of administrative intervention on zombie firms to explain why the selection effects are non-significant. We find that zombie firms in cities higher in the administrative hierarchy and those with a higher economic development zone index have a higher survival probability. Therefore, this article provides the following policy implications. First, local governments should consider industrial, firm and regional characteristics and rationally plan the industrial spatial layout when implementing industrial policies. Second, to promote the healthy development of industrial agglomeration, a market environment characterized by fair competition should be created for private firms and foreign-owned firms. Third, local governments should allow the market to play a basic role in allocating resources. Low-productivity firms should not be rescued by administrative means, as this could hinder the entry of high-productivity firms and the exit of inefficient firms. AUTHOR’ CONTRIBUTIONS All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Wenwen Wang. The first draft of the manuscript was written by Wenwen Wang and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. CODE AVAILABILIT Y STATEMENT The code that support the findings of this study are available from the corresponding author upon reasonable request. ACKNOWLEDGMENTS We would like to thank Professor Miaojun Wang, Professor Xiwei Zhu, Professor Xiangrong Jin, and seminar participants at Zhejiang University. Our deepest gratitude also goes to editors and anonymous reviewer(s) for their careful work and thoughtful suggestions. CONFLICTS OF INTEREST The authors declare that they have no conflict of interest. 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG | WANG DATA AVAILABILIT Y STATEMENT The data that support the findings of this study are available from the corresponding author upon reasonable request. ORCID Wenwen Wang https://orcid.org/0000-0003-2758-6606 ENDNOTES 1 This is the cost for products only sold within its city. When products are sold outside the city, the transportation cost should also be considered. 2 For the specific proof, refer to Combes et al. (2012). 3 We also use programs in the online appendix of Brandt et al. (2012) to match firms over the years. 4 The divided area’s city size cannot be measured in terms of previous urban populations. Li et al. (2019) believe that the number of firms can be used as a proxy for the urban size. Therefore, this paper sums the number of firms in different sub-regions to measure the scale of different space units. 5 In 2014, the State Council divided cities into five categories and seven tiers. Cities with a population greater than 10 million are considered mega cities; cities with a population of 5-10 million are considered super cities; cities with a population of 3-5 million are considered type I large cities; cities with a population of 1-3 million are considered type II large cities; cities with a population of 500,000 to 1 million are considered medium cities; cities with a population of 200,000 to 500,000 are considered type I small cities; and cities with a population less than 200,000 are considered type II small cities. 6 In addition, this paper also uses the method proposed by Arimoto et al. (2014), constructs an index to measure market access, divides the sample into two groups according to the degree of market access, and further tests the agglomeration and selection effects of prefecture-level cities with different market access levels to examine whether market integration affected the significance of the selection effects. 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See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 422 | 423 APPENDIX TABLE A1 Industry name corresponding to the 2-digit industry code 2-digit industry code Industry name 2-digit industry code Industry name 13 Food Processing 27 Medical and Pharmaceutical Products 14 Food Production 28 Chemical Fibers 15 Beverage Production 29 Rubber Products 16 Tobacco Processing 30 Plastic Products 17 Textile Industry 31 Non-metal Mineral Products 18 Garments and Other Fiber Products 32 Smelting and Pressing of Ferrous Metals 19 Leather, Furs, Down, and Related Products 33 Smelting and Pressing of Nonferrous Metals 20 Timber Processing, Bamboo, Cane, Palm Fiber, and Straw Products 34 Metal Products 21 Furniture Manufacturing 35 Machinery and Equipment Manufacturing 22 Papermaking and Paper Products 36 Special Equipment Manufacturing 23 Printing and Record Pressing 37 Transportation Equipment Manufacturing 24 Stationery, Educational, and Sports Goods 39 Electric Equipment and Machinery 25 Petroleum Processing, Coking Products, Gas Production, and Supply 40 Electronic and Telecommunications 26 Raw Chemical Materials and Chemical Products 41 Instruments, Meters, Cultural, and Official Machinery 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License WANG ***p < .01; **p < .05; *p < .10. −0.029*** 0.000 4,713.85 20,479 YES (−27.673) 2 0.000 671.8 4,091 YES (−3.761) −0.226 *** Stated-owned 3 −0.029*** 0.000 759.7 3,756 YES (−10.656) 4 0.000 929.61 10,831 YES (−1.031) −0.019 Foreign-owned 5 −0.031*** 0.000 1,496.16 9,869 YES (−21.398) 6 0.000 1,328.85 7,265 YES (−2.999) −0.158*** Private-owned 7 −0.028*** 0.000 1,391.85 6,854 YES (−12.289) 8 WANG 14682257, 2021, 1, Downloaded from https://onlinelibrary.wiley.com/doi/10.1111/grow.12430 by Zhejiang University, Wiley Online Library on [13/07/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License 0.000 4,397.81 LR Chi2 Prob > Chi2 22,187 YES (−2.098) −0.058 Observations Control variables Zone_index Rank ** All samples 1 Further exploration of nonsignificant selection effects using cox survival analysis | TABLE A2 424