M.I.T. LIBRARIES - DEWEY Digitized by the Internet Archive in 2011 with funding from Boston Library Consortium IVIember Libraries http://www.archive.org/details/labormarketimperOOacem 531 .M415 .n- working paper department of economics LABOR MARKET IMPERFECTIONS AND THICK MARKET EXTERNALITIES FROM INNOVATION massachusetts institute of technology 50 memorial drive Cambridge, mass. 02139 LABOR MARKET IMPERFECTIONS AND THICK MARKET EXTERNALITIES FROM INNOVATION Daron Acemoglu No. 93-14 Oct. 1993 r»—MWIT^.^.. - M.I.T. DEC . J^.n—m LIBRARIES - 7 1993 RECEIVED ., # 93-14 LABOR MARKET IMPERFECTIONS AND THICK MARKET EXTERNALITIES FROM INNOVATION Daron Acemoglu Department of Economics, E52-371 Massachusetts Institute of Tectinology Cambridge, 02139 MA First Version: June 1992 Current Version: October 1993 JEL Classification: 031, E24 Keywords: Search, Innovation, Training, Thick Market Externalities Abstract When labor market imperfections are important, workers (and firms) do not receive their marginal product. This is shown to imply that the adoption of an innovation that increases the non-firm specific marginal productivity of a worker creates a positive externality on other firms. The presence of this externality can lead to a multiplicity of equilibria whereby in the inferior equilibrium innovation is not profitable because the workforce is untrained (unskilled). This mechanism illustrates how labor market conditions influence investment and innovation activity thus offering new links between unemployment and growth. These links also imply that when the entry decisions of firms are endogenized a further thick market externality is created since entry, by reducing unemployment, makes investment and further entry more profitable. Finally when firms are allowed to choose the timing of their innovation, free-rider effects are introduced and the Pareto preferred equilibrium disappears. full am grateful to Abhijit Banerjee, Charlie Bean, Oliver Hart, Michael Kremer, Chris Pissarides, Kevin Roberts and Andrew Scott for useful comments. I also thank seminar participants at Boston College, LSE, Northwestern, MIT, Princeton, Royal Economic Society Conference, University College London, University of Sussex and Yale where a previous version of this paper was presented under the title, "Labor Market Imperfections, Innovation Incentives and the I Dynamics of Innovation Activity". All remaining errors are mine. 1) Introduction Innovations and investment in new technology among the major channels activities are often thought as a major are likely to be of growth in the economy and cyclical changes in these When driving force of economic fluctuations (e.g. Schumpeter (1939)). invest or to innovate depend on the actions of other firms which expectations become equilibria in in the self-fulfilling is possible a firm's incentives to economy, a multiplicity of and economies with similar fundamentals can exhibit vastly different growth and cyclical behavior. Two mechanisms that introduce strategic complementarities/thick market externalities in investment decisions have been extensively studied in the literature. First, in monopolistically competitive markets, the demand for a firm's product other firms implying that a given firm do so. These aggregate demand is more may depend on likely to externalities produce (or the production level of invest), when other firms have been investigated by Shleifer (1986), Blanchard and Kiyotaki (1987), Murphy, Shleifer and Vishny (1989). Second, productivity of individual investment may be increasing in the amount of aggregate investment, for instance because productive information spreads between firms. This type of technological externality has been analyzed It is in different contexts by Romer (1986), Durlauf (1991,1993), Acemoglu (1993). also possible to classify the search externality as the thick market externalities in returns embedded model of Diamond (1982) Diamond's economy is in this category, generated by the social increasing in the search technology. With the possible exception of Diamond's contribution, labor market interactions are not central to this literature. This paper argues that interactions in the labor market can be a source of an important additional externality. Most innovations are associated not only with an increase in the productivity of physical capital but also in the human capital of workers. becomes important to determine the increased human who would It therefore benefit from the future revenue stream provided by capital of workers. Additionally, the propensity to innovate is obviously a key ingredient in economic growth and the influence of the organization of labor markets on growth is an important theoretical and practical concern that has attracted very little attention (although the implications of growth on the equilibrium rate of unemployment have recently been studied by Aghion and Howitt (1992) and Bean and Pissarides (1992)). In this paper we analyze investment in new technology workers. This complementarity between physical and nature but forms. We it human that requires the training of capital can can also be interpreted as the workers learning to adapt to will additionally assume that there 1 be technological new in organizational always exists a positive probability that the employment a new relation will come to an end and either the worker or the firm will have to look for partner (see micro evidence suggesting the presence of high uncertainty for jobs, e.g. Leonard (1987), Davis and Haltiwanger (1990,1992), Blanchard and Diamond (1989,1990)). Despite such large reallocations and uncertainty concerning the future of the employment relation, complete markets in particular competitive labor and perfect credit markets, ensure property rights on the increased revenue stream due to the higher efficiently distributed, leading to first-best innovation require the worker to make a payment human capital of that workers are and training decisions. Efficiency would to the innovating firm equal to the present value of the increase in his future earnings, which, in the presence of complete markets, coincides with present value of the social benefit from training (Becker (1975)). frictions are important, for instance not receive his full due marginal product to costly search, the worker in his future relationships this result arises despite the fact that the firm labor market will anticipate that he and therefore and underinvestment. less than first-best subsidy, leading to undertraining emphasize that However when may will pay the firm It is important to and the worker are allowed to write complete contracts and the worker has access to unconstrained borrowing opportunities. This mechanism not only leads to less than optimal training and innovation incentives, but also introduces a strategic complementarity between the innovation decisions of different firms: whilst an individual firm faces higher private costs due to a lower training subsidy from it from high human also anticipates being able to extract higher surplus bargains in the if it possesses the new economy, the higher is differently, the higher is the the more profitable This is a it new the profitability of number of firms becomes that for each firm to market and It is in the the proportion of trained workers physical capital to an individual firm. Put adopt the innovation and train their workers, do so. is strong enough to lead to multiple Pareto-ranked equilibria. In the is low because the workforce has a direct result of low innovation incentives. unemployment in future caused neither by technological externalities nor by interactions Pareto-dominated equilibrium, innovation capital, new is workers source of externality affecting innovation and training incentives, distinct from those outlined above. in the product technology. Thus the higher capital workers, its economy We also show insufficient that the human higher is (or in the relevant sector), the lower is the marginal profitability of innovation which implies that high unemployment will be associated with slower growth. Consequently, more serious imperfections in the labor market can lead to slower growth via two channels: first by creating a larger wedge between social and private productivity and second by increasing unemployment. In search models, unemployment is usually decreasing in the number of firms that enter the market. unemployment, implies profits decreasing in the level of is The mechanism created by the entry decisions of firms; as which makes identified in this paper, that another novel strategic interaction more firms enter, investment and further entry become more profitable. Finally, unemployment when we allow is reduced and firms to choose the timing of their innovation activity, additional free-rider effects are introduced in the innovation decisions and destroy the favorable equilibrium, thus intensifying the inefficiency. The plan of the paper is as follows. The next section explains the basic externality in a two-period model and discusses the empirical relevance of the mechanism that this paper. Section 3 considers the is proposed in continuous time infinite horizon analogue of this model. Section 4 closes the model of section 3 and discusses the links between unemployment and growth. Section 5 illustrates the free-rider effects by allowing firms to choose the timing of their innovation and finally section 6 concludes, while the appendix contains 2) Search in the Labor Market and Thick Market Externalities a) A all the proofs. Two-Period Example Consider a two-period economy consisting of a continuum of firms and workers with that there is full risk-neutral, the discount rate is set equal to zero and the product 1 employment. All agents are market and is Workers and firms are matched one one so equal measure normalized to . to competitive. Each firm can initially produce y units of the single good of this at the start the output of of the its first period it has an option to invest in a new technology economy that will increase production process to y -I- a in both periods. However, workers in this economy do not possess the necessary human capital to work with this new technology and hence they need to be trained in order for the new technology to be productive. Note that the increase the output of the firm is in independent of the number of firms that adopt the innovation. This assumption rules out both technological and aggregate demand externalities as the revenue of the firm this is independent of the number of firms investing in the new mechanism enables us to emphasize the The installation suggesting that of this new investments argument does not depend on cost for each worker is c, innovation opportunity be trained technology is suggested in this paper. assumed to cost 6. is which we only use assumed to only available at the in either period. technology. Although restrictive, Although there is evidence are often bulky (e.g. Cooper and Haltiwanger (1993)), our this aspect which is new The human be to simplify the analysis. The less than the incremental output; a. start of the capital that the first training While the period, an untrained worker can worker acquires will in general have firm- specific and non-firm-specific components. The firm-specific part of our concern in this paper as assume that some would be able to human work with an we assume analysis, be written between the firm and the worker new technology part of this human capital is not will not lead to the effects discussed in the introduction as long it as comprehensive contracts can Since the adoption of a this human Crucial to our mechanism is economy is considered, Becker (1975)). it plausible to is worker who can run a new machine capital is general: a identical that all the across the (e.g. machine owned by a different firm. To simplify the capital that the worker acquires the inability of workers and firms to general. is make their relationship continue as long as they desire; unavoidable separations are possible. Empirical evidence suggests separations and job destruction to be an integral part of the labor market (e.g. Leonard Diamond (1987), Davis and Haltiwanger (1990,1992), Blanchard and Krueger (1991)). For instance Blanchard and Diamond (1989) report workers move jobs per month and Leonard (1987) shows reallocation, as model much this situation as 4.5% of by assuming Haltiwanger (1990,1992)) all end of the at the another region, sector or firm'. To first may have to the example as simple as possible we assume this to by stochastic events. In general there market in the is that there are no new is arrivals. second period, labor will be traded in a Walrasian market and However we are not interested such a move can be made sufficiently he this equals the (it is assumed that trained or not, implying that competitive bidding will allocate ' that this competitive and workers have access the "right" workers to the "right" firms as trained workers are worker learns over time and will also second period, but again to keep saving the firm makes by hiring a trained rather than an untrained worker know whether a worker to happen with fact that firms a trained worker will receive an amount c more than an untrained worker, since firms move have a predetermined length, but instead the where the labor market to perfect capital markets. In the we assume two assumptions capture the actual duration of the relationship is determined We period and as a result disappear (shut-down) to leave this firm for instance die or their relationship will First consider the case absence of sectoral in the shocks (as evidenced by Davis and simplify the analysis probability d for each worker as well. These be new workers and firms who come even that close seven million workers are separated from their jobs every month. that firms face idiosyncratic with probability d. Similarly workers workers cannot make sure that (1990), Blinder and is in voluntary quits more valuable for firms that have caused by a better wage offer because unattractive for the worker by an exit fee. Yet if the not happy with this firm or that his talents will be put to better use in another sector or firm, an exit fee will not solve the problem, see footnote 3. adopted the innovation). In the first period, workers realize that if they are alive, they will obtain an additional c in the second period. Thus each worker would be willing to subsidize their firm for the increase in the present value of his future earnings by partly paying for his training, for instance by taking a wage below from the perfect capital markets worker's earnings is and posting a bond. The increase in the present value of the equal to (l-d)c as with probability d he will not be in the market. other side of the market, if by a-c, next period by borrowing his marginal product in the first period or (as it it invests, the firm will increase will revenue by a, its On the period and this have to pay a higher wage to get a trained worker or hire an untrained worker and pay for his training). But this second period return will only accrue to the firm if it when is the not destroyed. Thus sum of its present value is (l-d)(a-c). It be profitable will the increased revenue this period, the expected value of higher revenue next period and the subsidy paid by the worker exceed the current cost which investment is to invest only profitable iff (2-d)a>5+c, is 5+c. Thus also the optimal decision rule for this economy. Therefore despite the uncertainty concerning the future of the employment relation, the competitive markets allocate resources efficiently because after separation both parties obtain their full marginal product. Let us now turn to a labor market with matching frictions. In the second period workers without a firm and firms without a worker will search for partners and get matched together. However frictions Further as we imply that after the initial match neither party can costlessly change partners. are considering a two-period model, it is not possible to turn look for a better partner, thus a trained worker will accept a job use of his skills. This is however not crucial to our in down a match and which he cannot make best argument (see below). This imperfect mobility creates a surplus between these pairs and ex post bargaining over this surplus will determine wages. For simplicity whole surplus and wages are let set to us assume that the match-specific surplus a proportion /3 of this. is equal to the Also to demonstrate that rather than capital market imperfections that drive our results, we assume that it is labor workers have access to a perfect capital market and enforceable contracts between the matched pair can be written. These two assumptions also imply of property rights between that a simple reallocation the firm and the worker cannot solve the problem. This economy is is analyzed backwards starting from the second period. If a trained worker matched with a firm who adopted the innovation y-l-Q!. Thus, the wage paid to a trained worker untrained worker is is in the first period, the total surplus will w'=fi(y+a). On the other hand, matched with a firm possessing the new technology, the be when an total surplus is y firm does not train the worker. if the The assumption that firms and workers can write complete contracts implies that the firm should get the marginal return to w"=6y untrained worker receives Finally if the firm did not innovate in the the wage w°=By. that Now it pays to assume not, the proportion that a proportion worker will still As matching (1-d). is same result if period, then the total surplus w"=B(y +a-c)). is equal to y and trained or not, is income of a trained worker be is alive. Conditional is given by of the firms are expected to innovate. Since no new not conditional upon whether the firm has the new technology on this, in the </>. who possesses second period^ conditional on being alive now he will stay with the firm with probability the new 64) is just he will be technology. Thus his expected income The expected is [(l-d)+d<^]fi(y-l-a)-l-d(l-</>)By. income of an untrained worker on the other hand Let us or second period. With probability (1-d) completely random (see discussion below), with probability separated but matched with a firm in the <i> training decision; thus the of firms looking for a match in the second period will also be calculate the expected the first the worker, irrespective of whether he its firms arrive and firm death we get exactly (incidentally, its Thus By. the expected increase in the present value of the worker's earnings SB=(l-d)(l-d+d0)Ba, is the subsidy (bribe) that the worker On willing to pay to the firm in order to receive training. the other side of the market, the firm will receive the full marginal benefit of innovation, a, in the wages is (see footnote 2) first and period. it However, may have in the second period it will to incur the training cost again if a have to pay higher new worker who is untrained arrives. Thus the expected present value of the increase in the firm's expected revenue in the second period, AR, is AR=(l-d)[(l-d-l-d0)(l-B)a+d(l-0)(a-c)] where the first term on the right-hand side with a trained worker. The second term which has probability d(l-<^) since their workers in the first period is is its the profit that the firm net profit a proportion <A when matched with an if the l-</) ^ is greater than the cost, together untrained worker, of newly unemployed workers will sum of the incremental return in the period, a; the increase in the expected return in the second period, paid by the worker, SB, it is of firms adopted the innovation and trained and hence a proportion be untrained. Innovation will thus be beneficial makes when AR; and first the training subsidy 8+c. Collecting terms we obtain the following The assumption that even if the worker stays with the firm, he receives w' is a convenient normalization as the worker pays the expected value of this increased salary back to the firm form of a training/innovation subsidy. in condition for innovation to be profitable (2-d)a>8+c^d(l-d)(l-<f))c Inspection of (1) leads to a (i) There are insufficient incentives by "innovate (given the worker Some all number of iff (1) interesting observations; outcome to innovate relative to the competitive/first-best (2-d)a^5+c"). The underlying reason to capture all the future benefits created by this is the inability of the firm and innovation and training decision. of the future benefits accrue to \ht future employer of the worker. Underpinning this and the results of this paper are the following three assumptions: (a) the innovation in question necessitates upgrading the worker's general human capital which increases his future as well as current productivity; (b) there exists a positive probability that the worker will not be together with the same firm in the future; (c) labor market frictions prevent the competitive allocation of workers, thus imply that workers expect to receive less than their marginal product. The crucial ingredient here is the randomness of matching. This implies that we cannot make sure that the may "right" workers end-up with the "right" firms. Naturally in practice, trained workers to accept a job in which their skills are not being put to use. However, this refuse would not change our results as when trained workers meet a firm without the new technology, they will continue and incur a search cost and therefore they will be receiving to search product because of the search with the new technology and cost. As a result less than their fi^ll marginal workers will care about the proportion of firms similarly firms will care about the human capital of the pool of workers. (Although the main externality analyzed here remains, a number of different issues arise when we allow workers It is in this to change partners and model search costs employer (such as an is certainly not one between the worker and first-best its current exit fee), because all the spill-overs within this relationship are being taken care of by the existing training subsidy, SB^. By the return to the worker, but rather, that of the ^ It what arrangements would restore instructive at this stage to contemplate economy. The required subsidy explicitly). its training decision the firm is not increasing worker's^ure employer. Therefore, a payment can also be noted that if the worker did not die but just moved to another sector, region or firm because of some exogenous reason learned that the match specific surplus specifying an exit fee can be written. is (e.g. he is no longer productive with this firm or small in a Jovanovic (1979) type setting), a contract However it can easily be seen that this will not change The value of the exit fee needs to be subtracted from the subsidy, SB and added to AR and these two will exactiy cancel out. The crucial point here is that the quit is not because of anything. a high wage offer but because it is optimal (or unavoidable) for the worker to move. from the future employer of the worker to his current employer is Since such a required"*. subsidy cannot be easily implemented by the market, decentralized equilibrium will often where the to internalize this externality. Transfer markets for sportsmen provide an instance market implements such a scheme; the new team has to make a payment player. The a match between a firm with the The However two separate job as long as the probability of new technology and a worker with high human on the abundance of these types, the (ii) to the old club of the crucial ingredient for such an arrangement is the existence of markets, one for trained and one for untrained workers*. effects suggested in this paper will to the actual cost, The 5+c. However, with because the firm anticipates that can also see that . it depends capital be present. decision rule summarized in (1) can be interpreted as "invest iff the benefit than the effective cost of innovation" is effective cost in a competitive labor market frictions, may have we have fail greater is equal the additional term, d(l-d)( 1-0)0 of training to incur the cost in the future. this externality leads to natural multiplier effects since, as one firm Here we invests, it reduces the effective costs to other firms and they become more willing to invest. Thus a shock that makes investment more productive for a group of firms will also increase the profitability of investment for, and innovation activity by, other firms. (iii) since the effective cost of innovation Incentives to innovate are increasing in As more in this variable. firms innovate, the pool of trained workers grows and it is decreasing becomes more profitable for each firm to innovate. Therefore the interactions in the labor market create thick market (iv) externalities. Although the source of the externality is that workers (and firms) do not receive their full marginal products, the bargaining power, 6, does not affect the effective cost of training. This is because of our special set-up. In our model a trained worker loses (l-15)a when he meets a firm with the new new technology "* technology, however this extracts when it is exactly equal to the the future employer of the worker distinguishes this effect (1984) where bargaining only over wages may lead investment it less them and from the one discussed by Grout to investment increases the quasi-rents obtained by the workers. wage that the firm with the meets a trained worker. However, the worker also receives The fact that the externality is not between the worker and solved if binding amount the firm but between underinvestment because higher However such a problem can be contracts can be written or workers can subsidize the firm for the undertakes. Our externality does not require these restrictions on bilateral contracting opportunities. Saint-Paul (1993) and Burdett and Smith (1993) discuss returns to education of such market segmentation. * 8 in the presence than his marginal product because with a positive probability he ends-up with a firm make good use of bargaining power enters the decision rule, but if cannot worker and the firm face different probabilities of death, his skill. If the becomes more important who effect is of second-order. its However, bargaining workers have to make their human capital decisions before meeting a firm. We can now summarize the main result of our discussion; Proposition 0: If 6-l-c<(2-d)a<5-l-c-l-d(l-d)c, there exist economy; one in which the other in which all firms adopt the innovation in period no innovation nor Returning to (ii) two pure strategy symmetric Nash above, the intuition of our result can be given as follows; from which anticipates that the workforce, line with is the workers and train their training take place. firms do not invest, the effective cost of training This and 1 equilibria in this view that certain investment because their workforce for protecting infant industries; is its come, will be low human developed countries do not attract untrained and unskilled (a similar argument for a discussion other prohibitively high for the firm as is future workers less when is it capital. sufficient also used see Johnson (1971) or Corden (1974)). However, as firms who adopt the innovation would often find it profitable to train their new workers, the general level of training in the workforce will be endogenous and in order to analyze this problem fully we need a dynamic model which Finally, since the equilibrium in welfare can be improved in this which the innovation economy by subsidies may vary between For shows new Pareto inferior, many countries and our that the need for training in some firms who would not adopt require to be targeted for such subsidies. by a monopolist, the monopolist may try a discount in order to entice firms into adopting the innovation. It is often observed that * to offer < 1) is instance, industries with high d or a high degree of heterogeneity (which would imply that there will always exist the innovation, thus in the next section. not adopted common that justifies these but also sectors. is develop subsidizing training or the adoption of the innovation*. Training and re-training subsidies are quite model suggests a mechanism we Alternatively, if the innovation is being supplied softwares offer discounts at early stages which is consistent with such a story. However, such action by a monopolist will not in general eliminate the externalities in our model. b) Empirical Relevance Since this paper to ask assume whether this new proposing a is mechanism is externality affecting investment decisions, empirically plausible and relevant. First that there are mobility costs in labor markets, in particular for high workers spend a long time without a job after a separation (e.g., infinite Most capital. Devine and Kiefer (1991) or in changing jobs. in hiring activities (Barron et al (1985)). Further, the empirical literature on job reallocation and gross worker flows uncertainty surrounding the future of plausible to is human Topel and Ward (1992)) and there also exist adjustment and transactions costs Firms also spend considerable resources it we have employment is indicative of significant As a rough measure, we can relations. use an horizon version of equation (1) with discounting which would imply that the effective cost of innovation is higher by ^ — ^ when other firms do not invest, where R is the real R+d annual interest rate (which is the relevant discount rate since capital markets are perfect). Given monthly separation rates are as high 4.5% (see Leonard (1987), Blanchard and Diamond that (1990)) or annual separations run close to 50% US a year in manufacturing (OECD (1986)), a conservative estimate of d would be around .20, also bearing in mind that trained workers have lower turnover than untrained ones (Mincer (1988)). taking, the annual 4%, this would imply workers, which is that the cost is 66% higher when b other firms do not train their an economically significant magnitude. Our mechanism instance that workers stay despite the of training real interest rate to is also consistent with a who number of findings switch jobs in general experience slower moving premium (Mincer (1988)) and that training fully (Bishop (1991)). Both of these are predicted in the training literature. wage growth who than those workers do not pay for For their general by our model as workers receive less than their marginal product once they change jobs. However, these findings can also be explained by interpreting all training as a combination of general and firm-specific training, hence cannot be used to conclusively endorse our mechanism. An alternative line of attack is to investigate whether there exist cases in which training costs played a crucial role in adoption decisions and whether thick market externalities important in this process. With this aim in mind, innovations. we turn Fichman and Kemerer (1993) discuss Methodologies), 4GLs to the adoption of software engineering three of them were innovations; (Production Fourth Generation Languages), Database Management Systems). Of these innovations only the all initially were thought to be very promising. SMs last and SMs (Structured RDBs (Relational one was adopted although in particular were hailed as "a revolution in software engineering" and had the capacity to bring "significant reduction in 10 systems maintenance costs" (Fichman and Kemerer (1993)). However, very few companies put them to to practice and they were soon abandoned. The only be high training costs. Although the benefits appear (as discussed in Section 5) may have been the key. significant disadvantage of to be potentially large, free-rider other explanations can also be offered to account for the failure of However seems effects Very few companies ended-up adopting innovation which would have increased the effective cost to those few that are often put SMs who went this ahead. Yet SMs; two obvious candidates forward are network-externalities' and learning from others' experience. there are no obvious reasons significant since standardization does not why technological network externalities should be seem to be as much an issue as in communication systems. Also since initial expectations were very high and the physical investment required was not very expensive (though the training costs were high), waiting to learn from others' experience may not be a very good explanation either. Turning to 4GLs, these were expected to bring "ten-to-one improvements in programming productivity" compared to COBOL and other 3GLs. Additionally these new techniques did not have compatibility problems when switching from 3GLs and the actual training costs were not high. Again, the two conventional explanations do not appear satisfactory. There was no need for networking; different companies used different programming languages before the arrival of 4GLs and as the set-up and actual training costs were low, waiting should not have been an important versions of 4GLs arrive the other hand, However, many different arrived in the market and each different language required additional training, thus the effective cost of training who would deterrent. was much higher than from companies RDBs that that the actual cost because new employees adopted other languages would have to be re-trained. had a very similar background to 4GLs and adopted and became the dominant technology. This is SMs were despite the fact that RDBs On very quickly required very expensive software and training, thus the response of the whole industry seems to be the key here. All three stories are consistent with our theory, while not easily explained by the alternatives. It is also possible to obtain historical examples. An attractive one for our purpose is the QWERTY keyboard discussed by David (1985). This is obviously an inferior technology adopted ' It can be argued that our externality is a form of network externality, as coordination also a key issue in our mechanism. Although this is mechanism is explicitiy derived from microfoundations and interactions in the labor market. With network externalities, we refer to those technological in nature (such as standardization in communication). For an analysis of network externalities, Katz and Shapiro (1986). 11 is partiy true, our at the time to slow down typists so as not to jam the typewriters. Also, there about the success of alternative keyboards and no need to standardize since the final output. However, QWERTY if it is obviously requires 3) is no need to low, the effective cost would is relatively only a few companies changed their keyboards. Thus a number of suggesting that uncertainty mattered was all that has survived to the present. Although there standardize the output and the actual cost of training be very high was no different pieces of empirical evidence accord well with our story, empirically relevant and plausible while much more its exact quantitative importance careful empirical investigation. The Basic Dynamic Model Consider a dynamic analogue of the economy of the last section. This economy consists of a continuum of risk-neutral and profit-maximizing firms with measure F, and a continuum of workers with measure F is small relative to produces goods worth Each firm At the firm y-l-b. is assumed to For simplicity and in contrast to the it not an assumption that changes our results, but it do not have to follow the time path will therefore employ a large number of workers level, there are constant returns to scale workers have no bargaining power (fi=0). As that is 1). 1. (thus and each worker previous section, we assume can be seen from the previous section, this we simplifies the analysis considerably as of wages for trained and untrained workers. Each worker be paid a wage rate equal to the opportunity cost of time which is assumed be to constant and equal to b. This also implies that the firm will pay for training as the worker is receiving none of the benefits. We denote the number of workers that a firm employs at time random shocks to workers and firms, t by n(t). we assume a constant exogenous probability Instead of of involuntary separation for each pair such that at every instant sn(t) workers leave the firm and join the unemployment pool. The firm receives X applicants from is constant in this section, X too is constant. We assume the unemployed. that As unemployment new workers can start production as soon as they arrive thus the firm does not lose any output in the turnover process. employment of each firm follows The the law of motion n'{t)=X-sn{t) 12 (2) where The firm n'(t) is derivative of n(t) y >0 and workers accept all job offers as they always receive the same wage the employment economy from a point of steady state. We at At time t=0 we are a steady in install the a cost c per worker. demand externalities the applicants* since all rate. In steady state n(t)=n=X/s. In what follows our how will later discuss state with n(t)=n available. This innovation will raise the product per but the firm needs to accepts both the number of number of workers per firm can be endogenized. firms in the market and the at be constant level of a typical firm will will start becomes with respect to time. As new technology = X/s, worker by a for a cost 5 and at an innovation opportunity all future periods, to train the existing workforce no technological or aggregate in the previous section, there are and the incremental revenue per firm as a result of this innovation is independent of the number of firms. To proceed it with the analysis, innovates and by V(t) when it let the value of the firm at time all be denoted by J(t) when does not. Each period, (1-s) proportion of the workforce from the previous period remains with the firm and technology t workers are the same, V(t) X new workers arrive. Since without the given by the following asset value equation is (3) rV(t) -V'(t) =(1 -s)n(t)y + Xy where is r is the discount rate (remember already subtracted). However, no change in the return to Two issues arise that output per worker is y+b when n'(t)=0 and n(t)=n, we a firm without the when we analyze new will so that the will determine what it from innovation. returns will First, returns will We further assume be time to choose a do when untrained workers apply. The firm — that is the general skill (i.e. naturally accept all applicants irrespective of their level of training (as there cost to doing so). bill n(t)b technology. Therefore V=ny/r. workforce will be changing endogenously). Second, the firm needs which strategy wage have V'(t)=0 as there varying as the number of trained unemployed workers will not be constant level of the new >c where c is is will no opportunity the cost of training a newly r+s arriving untrained profitable, see workers. * this. Lemma However in section 5 worker (when and there is assumption makes it is like to not satisfied, innovation will never be profitable to train all another aspect to waiting; until then firms are The firm would These 3.1). This this when newly arriving untrained to innovate? This we will consider only allowed to adopt the innovation immediately after expand as much as possible, however labor market it frictions prevent frictions also allow firms with different productivity levels to coexist despite firm- level constant returns. 13 becomes available and once they carry out the investment, they The The cost of adopting the innovation is 8. train its existing On workforce. a quit, thus untrained workers, the firm also receives who total initial cost is 5+nc as the firm has to (a+y) the revenue side, the firm receives a net return equal to from each worker who has not the cost c for those will train the workers. total of As (l-s)n(t). X(y+a) from workers it is profitable to train the arriving this period but incurs are untrained. In order to monitor changes in future training costs, define q(t) as the proportion of untrained workers in the unemployment pool. Thus q(t) measure of the general skill level of the economy. However, because employed workers q(t) only, innovation will train all their the workers of firms who also workers, thus did not innovate. firm that did not innovate by m(t)'. X=ns which may we it is be trained or untrained. Firms skill that composition of starts from a point of steady state, therefore (4) -/ '(0 =n{a ^y) -/wc(l -q(t)) Intuitively, a firm that has adopted the innovation will always train costs will vary depending on the training from unemployment; by the firm has to incur nsc(l-q(t)). level of the new workers. workers, all its therefore in steady state the revenue of such a firm will always be equal to n(a+y). will arrive in a enables us to rewrite the value of an innovating firm as: rJ(t) its adopt the denote the proportion of trained workers The economy one not sufficient to keep track of only need to determine the We is we However, In steady state ns workers definition a proportion (l-q(t)) of these will be untrained and As new workers only come from unemployment, m(t) does not enter (4) directly but influences the evolution of q(t). In other words, q(t) and m(t) will vary over time. on the proportion of firms unemployed worker that adopt the innovation, finds a job, p and will The law of motion of q(t) <^, will and on the probability be given by (see the derivation of equation depend that an (5) in the appendix)'"; (5) qXt)=p(<f>(t)^(l-<l>it))m(t)-qit)) ' This is again related to our assumption that there does not exist market segmentation depending on skill use of their skills. '° m(t) and level, thus trained </)(t) will is constant in who cannot make best become more important in section 5. Since in this section it is assumed it becomes available, <^(t) is constant over time be adopted as soon as symmetric equilibria. that innovation can only and m(t) workers can be matched with firms 14 In steady state, entry into and exit from workers who join the unemployment pool, innovation and are therefore trained. unemployment occur come from 0(t) trained Of the firms that have adopted the A proportion (l-<^(t)) come from firms that did not innovate and a proportion m(t) of those are trained. Also a proportion unemployment are at the rate p. which explains the term. last It is q(t) who of the workers useful to note that p exit assumed is equal across trained and untrained workers. Relaxing this assumption would not change our but would complicate the mathematics considerably. results, Finally, the law of motion of m(t) is given as follows; «^ m'{t)=s{q{t)-m{t)) At each They instant, workers arrive at the rate s and a proportion q(t) of those are trained. also leave the firm at the rate s and a proportion m(t) of those are trained. profitable for a firm to invest if the net present value of investing the net return of investment, of motion of J(t), equilibria, Lemma we q(t) is and m(t) only check <i>{i) greater than V(0). To determine jointly. Since in this section =l we is this positive; i.e. if J(0)-5-nc, we need to solve the law 3.1: when all all the other firms in the innovation if economy lemmas, the proof of The terms + that constitute ao Lemma c^ be is n. — +/r , it is profitable to n are doing so. 3.1 is in the appendix. r(5/n+c) intuitively explained; is the flow cost of no workers leave. However, the firm also considers rsc/(p+r), a "tax" imposed on the firm by workers who leave. Innovation larger be and 0(t)=O. p+r As with will are only interested in symmetric For values of the productivity of the new technology, «>«(,= invest It The latter effect is for each worker, 6 is due is more likely, the lower is c, 5, s and to the fact that, although the training cost has to the fixed cost of innovation and once the innovation is adopted r and the be incurred all workers have higher productivity. This builds a type of scale economies into the innovation process. will The parameters cost, s and p enter the decision rule because, although they do not influence the actual (6+nc), they are crucial for the effective cost of innovation. Now consider how incentives to innovate differ when other firms do not invest. The "tax" imposed on the innovating firms will be higher because the pool of untrained workers 15 is larger. Lemma 3.2: For values of the productivity of the new technology, a^a.^sc+ — rS +rc , optimal not to it is n invest when no other firm invests. As ao<ai, we can Proposition in which The result all that ao<a<a,, there exist of two pure same effective cost of innovation dep>ends the effective cost. is On Symmetric Nash Equilibria, is we obtained in the previous on the average quality of the human the other hand, the of this human capital and the more willing section, strategy as the result the workers the firm expects to receive in the future. higher this section: firms adopt the innovation and the other in which no firm invests. intuition of this proposition is the The section. main 1: For values of a such one establish the The lower more firms is this average quality, the invest, the higher is the quality each individual firm to innovate. As this interaction also leads to multiplier effects in capital of in the previous response to changes in costs or productivity. In what follows we will sometimes refer to the equilibria of Proposition 1 as "good" and "bad" or equilibria supported by favorable or unfavorable conjectures. These names are appropriate since there is a clear Pareto ranking between these equilibria. Also the "good" equilibrium can be thought of as having a higher growth rate because an economy in the "good" equilibrium undertakes more investment than one in the "bad" equilibrium". In particular suppose that a is drawn from a probability of investment in the is distribution H(a) with support good equilibrium is [0, 0o=l-H(ao), and a^. It follows that the in the "bad" equilibrium, 6i = l-H(ai). The probability of investment can be thought as a measure of the economy's growth potential implying Not only is that the "good" equilibrium has higher growth potential since eo> 9,. there a multiplicity of equilibria under plausible circumstances (and without nonlinearities and/or externalities in technology), but also the multiplicity of equilibria illustrates " If generalized with repeated arrivals of innovations, the "good" equilibrium would have However repeated arrivals introduce mathematical difficulties as when the second innovation arrives, the economy is out of the steady state. Naturally with one innovation a higher growth opportunity, as when rate. we have here, the growth effect will be negligible. firms differ in their adoption costs, but the expressions available upon request). 16 We also obtain similar results become more involved (details are a phenomenon that capital are is thought to be important by complements in many economists; as physical and most production processes, a predominantly low can be thought to deter investment. However this intuition is not true when the skill levels are traded). Proposition a result and formalizes the innovation However, invest. 4) it is 1 skill level human capital this intuition; in the that they anticipate their future workers to all to such firm adopts be predominantly untrained. may have endogenously also asserts that this state why no "bad" equilibrium the reason is and of the workforce (as long as shows how labor market imperfections can lead Thus the "bad" equilibrium can be seen arisen because firms do not as an "underskilling" trap. Closing the Model So variables, p and X have been far F, n, some new the labor force a steady is is insights about the interaction of labor markets U state, normalized to will 1, this be constant. The we endogenize treated as exogenously given. If also is the rate at unemployment these and the innovation process can be obtained. Let us denote the measure of unemployed workers in p, workforce the labor market competitive because workers will always be paid the marginal product of their firms will have no reason to care about the general skilled human this rate. economy by U. Since As we are dealing with which an unemployed worker finds employment, defined as equal to the flow into employment over the stock of unemployment, thus p=XF/U will be constant too. The following results can then be stated; Proposition 2: The value of a firm that innovates, J(t), is decreasing in the unemployment rate of the economy. Proposition 3: The probability unemployment of innovation in the favorable equilibrium, Gq, is decreasing in the rate. Proofs of these two propositions can be found in the appendix. \ The mechanism that leads to this result is that the 17 unemployed workers are by definition Therefore, untrained". innovation. to that The end the higher result, unemployment, the higher is the effective cost of is a negative relationship between unemployment and growth, similar is of Pissarides (1990) and Aghion and Howitt (1992) where higher growth leads to lower unemployment through higher job growth. An autonomous creation. But here, the causation runs increase in unemployment not in the above mentioned ones. This is in line from unemployment growth will lead to slower Habakkuk's (1962) famous in to our model but thesis that tight labor markets lead to faster growth, which receives some casual empirical support. However, Habakkuk's contrast to interpretation that most technologies are labor saving and in tight labor markets are the driving force leading to innovations with what we know our theory maintains that innovations are complementary wages which seems not accord well MacLeod about the nature of most inventions (see that high in (1988), to labor, but we Mokyr (1990)), obtain this result because tight labor markets provide more incentives for workers and firms to invest. More generally, p, the probability that a worker finds a job, will be a function of the number of firms as well as the of search equilibrium models number of unemployed workers (e.g. Pissarides (1990)), firm and the unemployment rate in this economy. we Using the insight in the market. can endogenize both the size of each However we determination of unemployment and innovation incentives so are most interested in the we will adopt a number of simplifying assumptions and keep the size of each firm constant. Since out of a population of 1, nF workers are employed, the unemployment economy, U, rate in this given by is en u=i-nF This also implies that as an additional firm becomes active, unemployment We will also assume that there is a fixed cost is reduced by n. of entry for each firm, k(F). This cost is a function of the number of firms in the market which will enable us to capture congestion effects. These effects arise in search "crowded" and the probability profits that models because as more firms enter, the market becomes a given vacancy will be from opening a new vacancy. Our desire the analysis makes congestion effects. this unattractive for us. Instead As more and McAfee (1987)). of firms, '^ reducing expected keep the firm size constant we assume that k'(F) firms enter the cost of opening a new > in order simplify to incorporate these firm increases (e.g. Howitt We also assume that the market cannot support more than a certain F**** thus lim^_^o.ax k(F)=<x) It to filled falls, thus . Also like Pissarides (1985,1990) can easily be seen that even institution that could offer them if training they we will number make use of unemployed workers had access to an educational would be willing to pay less for it than employed workers and the qualitative results would remain unchanged. 18 a zero profit condition in order to close the model. However Pissarides assumes exists profit opportunities in the market, thus the number of vacancies is some date and make for firms to decide whether to enter or not at new technology the productivity of the obtain some of become it variable that makes more sense the initial investment but if higher than anticipated, these firms will be able to the rent. We thus assume that all will is jump a instantaneously adjusts to satisfy a zero profit condition. For our purpose, that there never available at t=0. for the fact that it will know entry takes place at t=-T. Firms The productivity of this innovation once the productivity of the new technology is not know which revealed. We new technology known ex We will be looking be drawn from a distribution H(a). Expectations Equilibrium of this economy, thus firms is a that ante except for the Rational equilibrium will be played will show that even once we condition on firms' conjectures about which equilibrium will be played, there will exist an more firms additional strategic complementarity: as The zero -'^{ r The becomes more profitable. form of profit condition will take the k(F) =-^ +e enter, entry r"'^(/(0,a,F) -5 -nc -^)dH{a)} (8) r •'"Xn right-hand side of this equation can be explained as follows: the firm receives the flow ny from t=-T to 0. Thereafter continues to receive ny. The it can refuse to adopt the innovation in which case present value of this profit flow, evaluated at t=-T, Alternatively if the productivity increment, a, is is it ny/r. greater the cut-off productivity level, a^, the firm will adopt the innovation, obtaining J(0,a,F), incurring the innovation and training cost 6-l-nc, a, and losing the flow income of the old technology. As we need to take expectations conditional that although worker is on a>a(,(F) which is not know the realization of what integration does. Note n does not depend on the number of firms, the probability that an unemployed matched with a firm, p, does the flow profits, J(0,a,F) depend on First, in (8) there conditional we do F and via this, the cut-off level of productivity, q!,(F) and too. can be two different cut-off points for the adoption of upon a given number of firms (i.e. believe they are in the "bad" equilibrium, the "good" versus "bad" equilibrium). number of firms by 19 in the this innovation When all firms market will be determined Jsc*—*rc r P\F)^r r where p depends upon F through equations The LHS increasing by assumption. falls, p increases and which is profitability is Note is is that all these equilibria are conditional may firms enter. Alternatively firms These curves can thus is everywhere unemployment enter, we irb(F) obtain more than once intersect greater than Xb(0), there will exist an equilibrium two additional active but more firms of innovation increases. Differentiating also an everywhere increasing function. which no firm The RHS of this equation (5). also increasing since as as Figure 1 illustrates. In particular, if k(0) in and (4) y equilibria with positive activity may also exist. upon the "bad" equilibrium being played once the expect to be in the favorable equilibrium, in which case the equilibrium condition becomes ;t(^.S.e-'7"r . (!!i^-^-S-nc-!Si)M(.).^^(F) * ^—^"= r We can •' ,^ p(F)*r n p(F)+r r see that similar effects are present here as well but there is also the added effect that the cut-off productivity level is a function of the number of strengthens the strategic complementarity that created by entry decisions. In general, the firms enter, X, the number of firms number of of each firm will shrink. This is economy, in this applicants per firm will is n, will also fall the effect of congestion active firms. This effect further we tried incentives through the scale economies discussed earlier. In this context way, it is it it relationship Also note will also reduce innovation Even when we model the congestion cannot be analytically determined which effect will dominate. instructive to return to the relationship to slower growth. state equilibrium size to capture with k(F). unemployment. As emphasized above, higher unemployment leads and hence depend on F and as more and the steady that if further entry reduces the equilibrium size of firms, effect explicitly in this (11) r to between investment and lower investment incentives Yet Aghion and Howitt (1992) detect an inverse 'U' shaped between growth and unemployment (i.e. a low level of unemployment can be associated with a low as well as a high level of growth) in a cross-country regression using OECD data, while Bean and Pissarides (1992) question the existence of any well-defined relationship. This lack of negative relationship between unemployment and long-run growth 20 in ' the data poses a potential challenge to one of the predictions of our model. first be remembered unemployment due (e.g. should it growth and unemployment are both endogenously determined and while that unemployment may lead high However, slower growth, to high growth may also lead Aghion and Howitt (1992)), thus to the creative destruction effects of raw correlations may not be too informative. Further, the endogeneity of entry decisions model serves to muddy i.e. s, and 5, c, H(q!) will lead to different levels of activity in their economies. unemployment their As matching technology, activity, i.e. F, increases, but each firm also becomes smaller, thus leading to lower investment falls incentives through the scale economies. with low growth. On Hence a low F the other hand as level of increases and unemployment can be associated unemployment falls, probability from unemployment) rises thus increasing the incentives to innovate for i=b,g). of technical progress model active p (the (i.e. is may from that technical progress (or growth). In contrast in our influences that the of Aghion and Howitt. In their model, the form lead to higher (or lower) unemployment. number of firms which exit 7r|'(F)>0 High growth can therefore be associated with low unemployment. Yet, note causality in our case is very different their our in the waters via the level of activity and the size of firms in the market. Countries will differ in their fundamentals, which high to Thus the driving force of model the "driving force" unemployment and through incentives of the firms (and the growth rate of the economy). It is the is the investment this, often argued that the organization of the labor market will have implications for the growth performance of an economy (going back at least to Habakkuk (1962) and perhaps mechanism just identified, running which such effects will operate. different look from unemployment to growth, provides a route through This analysis also generates certain testable implications from Aghion and Howitt (1992)'s inverse U-shaped at the relationship The as far back as Marx). relationship. In particular, if we between unemployment and growth, using sectoral data and controlling for sector/region specific variables (such as average firm size, training costs, general skill level of the workforce etc), there should be a clear inverse relationship. However, control for these variables, the relationship Finally, when our model innovation activity An improvement in shift is is may no move from closed, an interesting complementarity between invention and obtained due to the multiplier effects discussed in the previous sections. the invention performance of the statics (i.e. point A not longer be negative. economy can be captured by a right-wards of H(a), the distribution function of the innovation's productivity. comparative when we do we do Now consider local not shift from one equilibrium to another, thus in Figure to point B), F, the number of 21 active firms, will increase and 1 we unemployment the cut-off level for innovation will to fall. This complementarity implies that a shock which leads growth when drawn from a favorable distribution may not lead to growth when drawn from a less favorable distribution incremental productivity, a, can be greater than the (i.e., new cut- off level, a^, but below the old cut-off level, a^)- Therefore in economies with better innovation prospects, mediocre investment opportunities will be exploited while the economies that face same not true for is an unfavorable distribution for new technologies. This mechanism would further agglomerate initial technological differences between economies. 5) Timing of Innovation Activity and Free-Rider Effects In this section the basic model of section 3 to choose the timing of their adoption after they receive the opportunity rather than being faced with a "now or never" decision as in the previous sections. firms are maintained. Since firms have a timing decision, to adopt the innovation. If the answer we adopted. With this aim in mind, becomes available at The assumptions that the training and the marginal productivity of innovation, a, are equal across cost, c, the innovation cost, 5, all modified in one respect. Firms are allowed is is t=oo, this we ask when it will be profitable corresponds to the innovation never being write the payoff to adopting at time t an innovation that time t=0; W{t) =(1 -e -" )^ +e -" [J(t) (12) -S -(1 -m{t))nc] r Intuitively for the first is the first term in (12). workers. As a (l-m(t))nc and It t periods the firm gets the return of a firm that has not innovated which At time it receives J(t). be optimal in the case where W'(0) opportunity is If the firm incurs the innovation cost 6 but also has to train the proportion m(t) of the workers are already trained, will obviously Lemma t is Discounting to innovate at this to t only only incurs the cost time t=0, the second term in (12) if positive, waiting will W'(t)=0 (or when W'(0)<0). be profitable at t=0 when is obtained. In particular the innovation received. 5.1: a<a.=sc+ — n it is it not profitable for a firm to invest alone. 22 +rc (13) The intuition of this that the effective cost Lemma is an extension of our results in sections 2 and of innovation lower when more firms is their train We know 3. workers. By implication, the first firm to innovate will face a high effective cost as no other firm has yet innovated. Therefore, order to reduce its all other things being equal, the firm would prefer to wait for others effective costs. However, by waiting the firm revenue which obviously has a cost. will If dominate and the firm will prefer same as condition in firm will find when it is do not want it to move first is 3.2 that each However is profitable because reduced. Yet, by the same reasoning those first. us that if 1 tells a>ao, will be when (13) there will exist is satisfied. two symmetric Without equilibria. possibility of waiting, there exist other possibilities: all firms can adopt the innovation t=0 or together at first the would bear a disproportionate share of the burden, thus they do not want the option to wait. Proposition go is will prefer to wait for others. can view firms as trying to free-ride on others. Waiting Next we can ask what the form of the equilibrium With the Also note that (13) we know from Lemma go alone and they to its (13) is satisfied, the first effect believes other firms will not be investing. as other firms invest the effective cost of training firms that adopt i.e. if (13) does not hold, profitable to invest even if we not too high, delaying the increase in to wait for others to innovate'^. Lemma 3.2; when (13) is satisfied, firms Alternatively a is in and the even when all a only a proportion of firms, indifferent between adopting rest follows slowly. However, Proposition 4 shows other firms adopt the innovation, it will when a > ao) and when (13) delaying, is satisfied, be profitable to wait, thus free- riding on the training costs. This implies that the favorable equilibrium in disappears (even that now and which the innovation the ineffficiency of the previous sections is is adopted intensified (proof of Proposition 4 in the appendix). Proposition 4: When and firms can delay adoption the innovation all firms innovate together The first to when (13) is is never adopted in equilibrium if (13) is satisfied not satisfied. intuition is given in terms of the free-rider effects. Firms would not like to be the innovate because the others would free-ride on the costs of training the workforce. But " For instance, in may gain a competitive edge, e.g. Fudenberg In practice there will naturally exist other considerations. markets, the firm that innovates first Judd (1985) and Tirole (1990) for a review of the 23 literature. oligopolistic et al (1983), when all other firms invest, each firm would still and wait for the training like to free-ride move of the workforce to increase sufficiently. As a result no firm wants to effectively blocks the innovation. effects Thus the and increases the inefficiency in the flexibility to level which first choose the timing creates free-rider model by destroying the favorable equilibrium. This can also be interpreted as creating inertia in the economy in response to new technologies as no one wants to move which is in some respects similar to (though Mokyr's concept to technological progress" what Mokyr (1990) dubs as "resistance much is richer as it includes creative destruction effects). 6) Conclusion The determination of investment and innovation and economists have been analyzing the market imperfections give that labor equilibria and free-rider effects. incentives is an important research area effects of externalities in this process. This paper rise to such externalities which The model we consider can explain may how shows lead to multiple skill shortages can endogenously arise making future investments less likely and also suggests some new linkages between unemployment and growth. A major shortcoming of our analysis ignored. Although change our results, it was informally argued it of future research that will be instructive may be is that the wage determination process was that effects through to analyze this wage determination would problem fruitful is to empirically test largely in some of more detail. not Another area the results implied by this model, in particular those relating to the link between unemployment and innovation incentives. Although our model predicts in contrast to low unemployment can be associated with high or low growth, Aghion and Howitt (1992) as the size of firms), lower tested that it implies that if unemployment on aggregate data but on we control for all other factors (such will lead to higher growth. This cannot sectoral or regional data, it be easily should be possible to investigate whether, controlling for the size of firms and skill-level of the workforce as well as fixed effects, the level of unemployment affects investment and productivity growth adversely. 24 Appendix Derivation of Equation (5): Let Q(t) be the number of trained workers in the unemployment pool and M(t) the number of Then trained workers in a firm that has not innovated yet. (Al) Q'(t)=nsF<i>(t)^M{t)sF(\-<l>{t))-pQ{t) At each instant ns workers join the unemployment pool from each firm. <^(t)F firms have adopted the innovation thus their workers are trained. (l-0(t))F have not adopted the innovation yet and only sM(t) trained workers quits the unemployment pool become unemployed from at the rate p and thus pQ(t) pool. Divide both sides of this equation by p=nsF/U. This Proof of trained workers exit the U which is constant; unemployment write M(t)=nm(t) and note that gives us (5). Lemma 3.1: We are considering the case where 0(t) = The steady state value of q(t) variable, q, and these firms. Also each worker is equal to l. Thus our system reduces 1, that of J(t) one non-predetermined variable, J. If is to two variables q and n(Qr+y)/r. There is one predetermined the rational expectations path is unique, one initial condition should enable us to determine the time path of both variables and there one initial condition given by q(0)=0. A J. is unique rational expectations equilibrium path exists as the roots of the problem are equal to r and -p from equations (4) and (5). The solution takes the form of p+r ^^^> r q{t)=Ae-P'^l where A is a constant which we determine from the initial condition q(0)=0 as A=-l. It then follows that Jity-n^e-P'^'^^^^ p+r r and 25 (A3) my'^k'^^y) -n£L p^r r Innovation a>ao. is profitable if J(0)-6-nc is greater than V(0), which gives us the condition QED Proof of Lemma 3.2: In this case unemployed workers are always untrained. will (A4) be no change As there is a continuum of firms, there of trained workers in the unemployment pool and thus the in the proportion return to investing is rJ The if a>a,. is strictly increasing in p. p Proof of Proposition increasing in Proof of again given by V above, thus it is profitable to invest 2: that innovates, constant population, is is QED The value of a firm 00 ^^^^ =n{y-^a) -nsc -nac from not innovating return Proof of Proposition which ' Lemma is when As we all other firms invest, J(t), is given by (A3), are in steady state with a constant defined as equal to nsF/U. Thus p is given is number of firms and decreasing in U. QED 3: p and hence decreasing in U. QED 5.1: Differentiating (12) with respect to time WXt) =e Substituting from (4), e" We we -" [ny -rJ{t) ^J'{t) ^rS^mc -mcm{t) +ncm ^^"^ '(/)] get W(t) = -na +nsc +nrc +r8 -nscq(t) -nrcm{t) +ncm are considering a firm that will innovate alone which implies that m'(t)=0. Substituting these in 26 ^^°' '{t) m(0)=q(0)=0, thus ^^^^ e" W'(t) = -na+nsc*nac+nrc+r8 This is positive if (13) is satisfied and the firm prefers to wait. Proof of Proposition Suppose (13) at time t? QED 4: is satisfied. Can we have an equilibrium This can only be an equilibrium if in which <^(t) firms adopt the innovation W'(t)<0. However, from (A8), W'(t)>0 irrespective of the value of 0(t) as long as m(t)=q(t)=0. Therefore at argument at all t, t=0 and by a similar every firm would prefer to wait further and in equilibrium, the innovation will not adopted. If (13) is not satisfied, innovation immediately at t=0. W'(0)<0 and QED 27 all firms find it profitable to adopt the References Acemoglu, D. 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