Advances in Management & Applied Economics, vol.3, no.2, 2013, 179-192 ISSN: 1792-7544 (print version), 1792-7552 (online) Scienpress Ltd Threshold effects in the capital asset pricing model using panel smooth transition regression (PSTR) Evidence from net oil export and import groups Chien-Chung Nieh 1 and Hsueh-Chu Yao 2 Abstract In this study, we used the PSTR (panel smooth transition regression) model to investigate the nonlinear relationship between beta (systematic risk) and returns (world market excess returns) for net oil export and net oil import groups. We set the volatility of world market excess return as the threshold variable and the percentage changes of crude oil price and exchange rate as the control variables. Our results support the use of a nonlinear model to elucidate the behavior both groups. We found that all beta values are positive and higher in the low regime (i.e., volatility of world market excess return is low) and lower in the high regime (i.e., volatility of world market excess return is high). For the net oil export group, the crude oil price change percentage is positive in the high regime, but the exchange rate percentage change is positive in the low regime. For the net oil import group, in both the low and high regimes, changes in crude oil price and exchange rate have equally positive effects on the individual market excess return. JEL classification numbers: G12, Q49, F3, C33 Keywords: CAPM, crude oil price, exchange rate, panel smooth transition regression model (PSTR), Schwarz's inequality, Triangle inequality 1 2 Department of Banking and Finance of Tamkang University, Taiwane, e-mail: niehcc@mail.tku.edu.tw Department of Banking and Finance of Tamkang University, Taiwane, e-mail: courtis_yao@hotmail.com Article Info: Received : December 5, 2012. Revised : January 3, 2013 Published online : March 15, 2013 180 Threshold effects in the capital asset pricing model using PSTR... 1 Introduction The well-known and widely used capital asset pricing model (CAPM) has been one of the most important models in finance over the last 40 years. Studies using the CAPM have demonstrated that beta or systematic risk is the only suitable risk measure, and additionally, that a positive linear relationship exists between beta and expected returns. Early empirical studies such as Fama and MacBeth (1973) tested the validity of the CAPM using a two-step approach. 3 They support the applicability of the CAPM for analyses of the U.S. stock market. However, a number of later studies have indicated that beta is not significantly related to return. In particular, Fama and Fench (1992) found that by analyzing a sample of U.S. stock returns data from 1963–1990, the results revealed not only a flat relationship between return and beta, but also announced the death of beta. Subsequently, many studies have shown that beta and return may not be related empirically because of bias created by the combination of positive and negative returns. Thus, Pettengill et al. (1995) used an alternative model to examine the validity of beta in measuring risk. In that study, the authors assumed that when the realized market returns exceeded the risk-free rate of interest (i.e., the realized market excess returns are positive or up-market), a positive relationship should exist between beta and return. Similarly, they also assumed that when the realized market excess returns are negative or down-market, a negative relationship should exist between beta and return. Hence, Pettengill et al. (1995) adjusted the approach used by Fama and MacBeth (1973) and developed a conditional relationship between beta and realized returns by separating periods of positive and negative market excess returns. The results of this adjustment show that for the period 1936–1990, there is a significant positive (negative) relationship between beta and realized returns when market excess returns are positive (negative) in U.S. stock returns. Following the statistical methodology by Pettengill et al. (1995), Fletcher (2000) examined the conditional relationship between beta and returns in (a) international stock returns from January 1970 to July 1998, and (b) the monthly returns of MSCI equity indices of 18 developed markets. Fletcher (2000) found a significant positive relationship in up-market months and a significant negative relationship in down-market months. Moreover, the relationships appear to be symmetric, and there is also a positive mean excess return on the world index. These results are consistent with those obtained by Pettengill et al. (1995). In addition, Tang and Shum (2003) employed the conditional framework to international stock markets and examined the conditional relationship between beta and returns for the period from January 1991 to December 2000. They also found a significant positive relationship between beta and returns in up-markets 3 In the first step, a CAPM is used to estimate beta. In the second step, portfolio returns are regressed on portfolio betas to test the relationship between beta and returns. Chien-Chung Nieh and Hsueh-Chu Yao 181 (positive market excess returns); however, they found a significant negative relationship in down-markets (negative market excess returns). As mentioned, these results imply the existence of a nonlinear risk-return relationship. Woodward and Marisetty (2005) applied a logistic smooth transition autoregressive (STAR) model to examine the beta non-stationarity issue in the Australian stock market. In doing so, they not only found evidence of a smooth transition between regimes using the 4-month-lagged yield spread as the transition variable, but also demonstrated the applicability of the STAR model. Similarly, Chen and Huang (2007) investigated the relation between stock returns and the world index for four Pacific Rim economies and found that the International Capital Asset Pricing Model (ICAPM) betas displayed regime switching based on underlying market volatility. Thus, the authors suggested that estimates of the ICAPM should account for the changes in betas over time and over different variance regimes. Finally, Woodward and Brooks (2009) examined the nonlinear relationship between beta and returns in 39 U.S. industry portfolios. Their empirical results also support the presence of a nonlinear relationship. With the growing interest in CAPM issues, a number of studies have further introduced alternate pricing factors, such as crude oil price and exchange rate, to investigate the relationship between beta and return. Basher and Sadorsky (2006) constructed an international multifactor model, which accommodated both unconditional and conditional risk factors, to examine the relationship between oil price risks and emerging stock market returns. Their results provide significant evidence that oil price risks affect stock price returns in emerging markets and suggest that the exchange rate risk factor is statistically non-significant. Additionally, the authors found that changes in oil price volatility have an asymmetric effect on stock returns. Nandha and Hammoudeh (2007) examined the relationship between beta and return with oil price and exchange rate factors for 15 Asia-Pacific countries by using the international factor model. Similarly, they indicated that oil price and exchange rate factors are both important for pricing individual stock market returns. Ramos and Veiga (2011) analyzed the exposure of the oil and gas industry to oil prices in 34 countries. Using a multifactor panel model to estimate the oil and gas excess stock returns, they strongly supported the view that oil price is a globally priced factor for the oil industry. Furthermore, beta, exchange rate, and oil price factors also have a significant impact on the oil industry’s excess returns. Thus, following both the nonlinear frame and the concept of alternate pricing factors shown in the literature, we apply the PSTR model, which was developed by González et al. (2004, 2005), to investigate the influence and nonlinear relationship between beta (systematic risk) and returns (world market excess returns) for net oil export and import groups. In our study, the volatility of the world market excess return is the threshold variable, and the percentage change of crude oil price and the percentage change of exchange rate are the control variables. Among panel data studies, Hansen (1999) initially introduced threshold effects, which included using a panel threshold regression (PTR) model. This PTR 182 Threshold effects in the capital asset pricing model using PSTR... model assumes that a transition between different regimes depends on the value of a selected threshold variable. Because the transition from one regime to another displays a sudden jumping effect when using the PTR model, and because the PTR model assumes that the threshold for regime switching is clearly defined and distinguished, results drawn by the PTR model may not accurately represent the market situation being investigated. To revise these drawbacks, we apply a PSTR model. This model allows for a gradual adjustment of the intermediate regime as the system moves from one regime to another among extreme cases. The remainder of this paper is organized as follows: Section II introduces the specifications of the PSTR model, and Section III presents a description of the data used in this study. Section IV shows the empirical results, and Section Ⅴ offers a conclusion. 2 Methodology González et al. (2004, 2005) developed the general panel smooth transition regression (PSTR) model, which is defined as follows: yit = µi + β 0' xit + β1' xit h(qit ; γ , c) + ε it (1) where i=1,…,N, and t=1,…,T. yit is the dependent variable, xit is the k-dimensional vector of explicative variables, µi proxies the fixed individual effect, and the error term is denoted by ε it . The transition function h(qit ; γ , c) is Following a continuous and bounded function of the transition variable qit . the work of Granger and Teräsvirta (1993), González et al. (2004, 2005) considered the following logistic transition function: −1 m with γ > 0 and c1 ≤ ≤ cm (2) h(qit ; γ , c) =+ 1 exp −γ ∏(qit − c j j =1 where c = (c1 , , cm )' is an m-dimensional vector of location parameters, and the slope of transition function is denoted by γ , which proxies the smoothness of transitions. Generally, considering m = 1 or m = 2 is sufficient because these values allow for the commonly encountered types of variation in the parameters. 4 For m = 1 , the model implies that the two extreme regimes are associated with low and high values of qit . When γ → ∞ , the logistic transition function h(qit ; γ , c) 4 m = 1 corresponds to a logistic function with an S-shape, and m = 2 corresponds to a exponential function with a U-shape. Chien-Chung Nieh and Hsueh-Chu Yao 183 becomes an indicator function I [ A] , which possesses a value of 1 when event A occurs, and is otherwise 0. Thus, the PSTR model in (1) is reduced to Hansen (1999)’s two-regime panel threshold model. For m = 2 , the transition function has a minimum of (c1 + c2 ) 2 and possesses a value of 1 for both low and high values of qit . Therefore, if γ → ∞ , the model becomes a three-regime threshold model. Finally, for any value of m , the transition function (2) becomes constant when γ → 0 , in which case the model is reduced to a homogenous or linear fixed effects panel regression. González et al. (2004, 2005) generalized the PSTR model to allow more than two different regimes, and constructed the additive model as follows: r yit = µi + β 0' xit + ∑ β 'j xit h j (qit( j ) ; γ j , c j ) + ε it (3) j =1 where the transition functions h j (qit( j ) ; γ j , c j ) , j = 1, , r , are of the logistic type (2). 5 The PSTR model building procedure consists of specification, estimation, and evaluation stages. Specification includes testing homogeneity and selecting the transition variable qit . If the tests fail to show homogeneity, Eq. (2) is employed to determine the appropriate form of transition function, that is, the proper value of m . A nonlinear least square method is used to estimate the parameters. During the evaluation stage, the estimated model is subjected to misspecification tests to examine whether it provides an adequate data description. The null hypotheses tested at this stage include parameter constancy, remaining heterogeneity, and autocorrelation of the errors. Finally, the number of regimes in the panel must be determined, meaning that a value must be selected for r in Eq. (3). 6 3 Data In this study, we set the volatility of world market excess return as the threshold variable and the percentage changes of crude oil price and exchange rate as the control variables to investigate the nonlinear relationship between beta (systematic risk) and return (world market excess returns) among 14 emerging markets. Next, according to data provided by the Energy Information 5 As Hansen (1999) highlighted, if m = 1 , qit( j ) = qit , and γ j → ∞ for all j = 1, , r , the model in (3) becomes a panel threshold regression (PTR) model with r + 1 regimes. 6 For a more detail, see González et al. (2004, 2005) or Colletaz and Hurlin (2006). 184 Threshold effects in the capital asset pricing model using PSTR... Administration (EIA), 7 we divided all markets into two groups 8: oil exporters (e.g., Colombia, Indonesia, Malaysia, Mexico, Russia, and Venezuela) and net oil importers (e.g., India, Israel, the Philippines, South Africa, South Korea, Sri Lanka, Taiwan, and Thailand). This study features a monthly sample period that spans September to May of 2011, with 117 observations for each variable. Sample markets information is shown in Table 1. Table 1. Stock price indices and risk-free rate employed in the study Market Colombia Indonesia Malaysia Mexico Russia Venezuela India Israel Philippines South Africa South Korea Sri Lanka Taiwan Thailand Market index IGBC INDEX Market risk-free rate 1-month interbank offered rate IDX COMPOSITE 3-month interbank offered rate FTSE BURSA MALAYSIA 3-month interbank KLCI offered rate MEXICO IPC 90-day money market RUSSIAN MICEX INDEX 90-day money market VENEZUELA SE GENERAL 30-day money market INDIA BSE (100) 3-month India T-bills NATIONAL TEL AVIV SE GENERAL 3-month Israel T-bills PHILIPPINE SE I(PSEI) 3-month Philippines T-bills FTSE/JSE 3-month South Africa T-bills KOREA SE COMPOSITE 3-month South Korea (KOSPI) T-bills COLOMBO SE 3-month interbank offered rate TAIWAN SE WEIGHTED 90-day money market BANGKOK S.E.T. 3-month interbank offered rate 7 Source data are available from their homepage: <http://wia.doe.gov>. 8 If a country’s oil export volume is greater than its oil import volume, it is categorized as a net oil export group; conversely, if a country’s oil import volume is greater than its oil export volume, it is categorized as a net oil import group. Chien-Chung Nieh and Hsueh-Chu Yao 185 To account for the volatility of world market excess returns, we used the MSCI world index 9 and constructed a proxy of the moving-average standard deviation for the percentage change of the world market excess return. 10 The percentage change of crude oil price data in the model is represented by the logarithmic change in West Texas Intermediate (WTI), priced in U.S. dollars per barrel. The percentage change of exchange rate data for all currencies is defined as the logarithmic change in currency rates against the U.S. dollar. Except for the crude oil price data, all data are extracted from the DATASTREAM database. The crude oil price data were obtained from the EIA database. Table 2 shows the descriptive statistics of all variables. Table 2: Summary statistics Mean Median Maximum Minimum Std. Dev. Skewness Kurtosis Jarque-Bera Sum Sum Sq. Dev. Observations Cross sections IERit 0.881255 1.173347 38.79845 -31.61199 7.101660 -0.315026 5.047692 313.2681 1443.496 WERit -0.333787 0.418272 13.48965 -22.44858 5.339821 -0.953404 5.318842 615.1334 -546.7429 VWERit 5.359381 3.940894 20.70533 0.451495 3.941785 1.951098 6.588259 1918.012 8778.665 ∆OPit ∆ERit 1.229173 1.944766 27.34475 -42.93591 9.893556 -0.883681 5.488764 635.9202 2013.386 -0.001574 -0.005686 69.31588 -34.89809 4.054526 4.650950 76.27072 372312.2 -2.577990 82559.77 1638 46676.92 1638 25435.17 1638 160233.6 1638 26910.94 1638 14 14 14 14 14 Notes: In this table we report the descriptive statistics of monthly individual market excess return ( ), monthly world market excess return ( ), monthly volatility of world market excess return ( ), monthly percentage change of crude oil price ( ) and monthly percentage change of exchange rate ( ). *** denote significance at 1% levels, respectively. 9 10 Following Tang and Shum (2003). Following Nieh (2002), a time-varying proxy for σ t to measure the volatility of world market excess return can be specified as: 0.5 m σ it = (1 m)∑ (log WERt +i -1 - log WERt +i -2 ) 2 , where WER is the world market i =1 excess return ( i =1, ,14 denotes the market and t denotes the time period) and m = 3 considering seasonal considerations. 186 Threshold effects in the capital asset pricing model using PSTR... 4 Empirical results Table 3 shows the stationary results of each variable using LLC (Levin et al., 2002) and IPS (Im et al., 2003) tests. 11 The results indicate that the null variable among the non-stationary variables can be rejected for any series level, which ensures an I(0)-type series. Table 3: Panel unit root tests IERit WERit VWERit OPit ERit LLC IPS Intercept Intercept&Trend Intercept Intercept&Trend -31.9166*** -34.9949*** -32.8845*** -33.2761*** -24.0072*** -23.9369*** -30.9666*** -31.1013*** -3.52020*** -2.83301*** -8.98482*** -7.96964*** -37.2324*** -41.6300*** -29.7843*** -29.7480*** -39.5655*** -44.5602*** -35.7457*** -36.6405*** Notes: In this table we report the descriptive statistics of monthly individual market excess return ( IERit ), monthly world market excess return ( WERit ), monthly volatility of world market excess return ( VWERit ), monthly percentage change of crude oil price ( ∆OPit ) and monthly percentage change of exchange rate ( ∆ERit ). LLC and IPS represent the Levin et al. (2002) and Im et al. (2003) panel unit root techniques. The 10, 5, and 1% critical values for LLC and IPS are: -1.65, -1.96, and -2.58. *, **, and *** denote significance at 10%, 5% and 1% levels, respectively. Next, we applied the PSTR model developed by González et al. (2004, 2005) to not only (a) set the volatility of world market excess return ( VWERit ) as the threshold variable and (b) the percentage change of crude oil price ( ∆OPit ) and the percentage change of exchange rate ( ∆ERit ) as control variables, but also to define the nonlinear relationship between beta ( β ) and individual market excess return ( IERit ), as follows: IERit = µi + α 0 ∆OPit + α1∆ERit + α 2WERit + ( β 0 ∆OPit + β1∆ERit + β 2WERit ) g (VWERit ; γ , c) + ε it 11 LLC is a modified version of the LL (Levin & Lin 1992, 1993) panel unit root technique. (4) Chien-Chung Nieh and Hsueh-Chu Yao 187 Before beginning the PSTR test, we examined a linear model and tested it against a nonlinear model with one threshold. By rejecting the null hypothesis, a single threshold model was estimated and tested against a double-threshold model. This process continued until the hypothesis of no additional threshold was not rejected. Table 4 shows the results of the linearity and specification tests for no remaining nonlinearity. Table 4: LM Test for Remaining Nonlinearity Country Number of Location Parameters Net Oil Export Net Oil Import m =1 m=2 m =1 m=2 = H 0 : r 0= vs H1 : r 1 17.091*** (0.000) 22.362*** (0.000) 40.909*** (0.000) 41.630*** (0.000) = H 0 : r 1= vs H1 : r 2 0.750 (0.862) 21.148*** (0.002) 3.509 (0.321) 12.517* (0.053) = H 0 : r 2= vs H1 : r 3 - 24.004*** (0.001) - - Table 5: Determination of the Number of Location Parameters Number Parameters Country of Net Oil Export Location Net Oil Import m =1 m=2 m =1 m=2 1 2 1 1 Residual Sum of Squares 25060 23806 28071 28084 AIC Criterion 3.6108 3.5896 3.4276 3.4313 Schwarz Criterion 3.6627 3.6869 3.4690 3.4779 Optimal Number Thresholds * r ( m) of The linearity tests clearly rejected the null hypothesis for linearity in both the net oil exporting and net oil importing groups, but the null hypothesis of r = 1 was not rejected at 1% significance for m = 2 concerning the net oil import group. In the next step, we selected the optimal number of location parameters for 188 Threshold effects in the capital asset pricing model using PSTR... the transition functions based on the Akaike criterion (AIC) and Schwartz’s Bayesian (SBC) criterion. Consequently, we consider all groups with m = 1 . These results are shown in Table 5. 12 Table 6: Parameter Estimates for the Final PSTR Models Country Net Oil Export Net Oil Import (m, r * ) (1,1) (1,1) Variables Coefficient estimate t-statistic Coefficient estimate t-statistic α0 -0.0728 -0.5846 0.0575*** 2.4088 α1 0.6760*** 2.2021 -0.0127 -0.1545 α2 1.7030*** 5.4551 0.9532*** 15.5308 β0 0.2890 1.6066 0.2168*** 3.1700 β1 -1.0620*** -2.2853 -0.3017 -1.4508 β2 -1.4147*** -3.6415 -0.7485*** -5.4687 c 2.2356 9.8750 γ 0.2512 1.3148 RSS 25060 28071 AIC 3.6108 3.4276 BIC 3.6627 3.4690 The parameter estimation results appear in Tables 6 and 7. For the net oil export group, the relationship between the individual market excess return and beta is shown to be positively related in two different regimes. The relationship is higher in the low regime (threshold value ≤ 2.24%) and lower in the high regime (threshold value>2.24%) . This suggests that a 1% increase in the world market excess return leads to an incremental 1.7030% increase in the individual market excess return in the low regime and a 0.2883% increase in the high regime. For 12 For more detail, see Enders (2004), pp. 69-70. Chien-Chung Nieh and Hsueh-Chu Yao 189 the control variables, the percentage change of crude oil price is negatively related (-0.0728%) to individual market excess returns in the low regime and positively related (0.2462%) in the high regime. Conversely, the percentage change of exchange rate is positively related (0.6760%) to individual market excess returns in the low regime and negatively related (-0.3860%) in the high regime. For the net oil export group, both the individual market excess returns and beta are positive; moreover, they are higher in the low regime (threshold value < 9.88%) and lower in the high regime (threshold value > 9.88%) for the net oil import group. The crude oil price percentage change is positively related in two different regimes, where the percentage change of exchange rate is negatively related. Table 7: Estimation of Coefficients of Control Variables in PSTR Models Country Net Oil Export Low regime Variables (c ≤ 2.24%) Beta 1.7030 -0.0728 0.6760 ∆ Crude Oil Price ∆ Exchange Rate Country High regime (c >2.24%) 0.2883 0.2162 -0.3860 Net Oil Import Low regime High regime (c >9.88%) Variables (c ≤ 9.88%) Beta 0.9532 0.0575 0.2047 0.2743 -0.0127 -0.3144 ∆ Crude Oil Price ∆ Exchange Rate Our main empirical findings are as follows. First, we found that all beta values are positive, and they are higher in the low regime and lower in the high regime. This suggests that beta has asymmetric effects on excess returns in individual markets. 13 Specifically, investors in stable circumstances (i.e., world market excess return is less volatile) can earn more risk premium than in unstable circumstances (i.e., world market excess returns are more volatile). Second, the result of changes in crude oil price has a positive coefficient in the net oil export group, which suggests that rising crude oil prices result in an oil risk premium increase. This outcome is in line with actual economic behavior. Generally, when oil-producing countries announce a reduction in oil production, 13 This finding is consistent with previous research. See Woodward and Marisetty (2005), Chen and Huang (2007), and Woodward and Brooks (2009). 190 Threshold effects in the capital asset pricing model using PSTR... the result is marked by market volatility. An oil price increase caused by a decrease in oil supply is ultimately beneficial for a particular stock market. In contrast, for the net oil-importing group, regardless of stable or unstable circumstances, changes in crude oil price have a positive effect on the excess return of individual markets. Furthermore, oil-dependent countries, oil producers, and oil investors are more concerned with information concerning changes in oil price because this information affects key production and investment decisions. Therefore, when oil prices increase, investors demand a higher oil risk premium. This is consistent with the evidence presented by Basher and Sadorsky (2006). Finally, as Narayan and Narayan (2010) argued, an appreciation in the exchange rate of an export dominant country reduces the competiveness of exports and is, furthermore, disadvantageous to the domestic stock price. For an import dominant country, an appreciation in the exchange rate caused by reducing input costs increases domestic stock prices. Therefore, for the net oil export group, our results demonstrate that changes in the exchange rate have a positive effect on individual market excess returns under stable circumstances. The implication here is that only when the exchange rate depreciates during stable conditions can an exchange risk premium exist. Moreover, for the net oil import group, individual markets experience exchange rate risk premiums, regardless of conditions. 5 Conclusion In this study, we used the PSTR model, developed by González et al. (2004, 2005), to investigate the relationship between beta (systematic risk) and returns (world market excess returns) for net oil export and import groups over the period from September to May of 2011. We used the volatility of world market excess returns as the threshold variable and the percentage change of crude oil price and the percentage change of exchange rate as control variables in our analysis. The results support a nonlinear relationship between systematic risk and world market excess returns, based on the volatility of excess world market returns. This suggests that beta has asymmetric effects on individual market excess returns regarding two groups: net oil exporters and net oil importers. Investors in the low regime (i.e., world market excess return is less volatile) can take more risk premium than investors in the high regime (i.e., world market excess returns are more volatile). For the net oil export group, we find that changes in the crude oil price that benefit individual market excess returns exist only in the high regime. In addition, exchange rate fluctuations have a positive effect on individual market excess returns in the low regime. Finally, for the net oil export group, the results indicate that for both the low and high regime, changes in crude oil price and exchange rate have a positive effect on individual market excess return. Chien-Chung Nieh and Hsueh-Chu Yao 191 References [1] S.A. Basher and P. Sadorsky, Oil price risk and emerging stock markets, Global Finance Journal, 17, (2006), 224-251. [2] S. Chen and N. Huang, Estimates of the ICAPM with regime switching betas: Evidence for four Pacific Rim economies, Applied Financial Economics, 17, (2007), 313-327. [3] G. Colletaz and C. Hurlin, Threshold effects in the public capital productivity: an international panel smooth transition approach, Document de Recherche du Laboratoire d’Economie d’Orleans, (2006). [4] W. Enders, Applied econometric time series, Wiley, New York, 2004. [5] E. Fama and K. French, The cross-section of expected stock returns, Journal of Finance, 47, (1992), 427-465. [6] E. Fama and J. MacBeth, Risk, return, and equilibrium: empirical tests, Journal of Political Economy, 81, (1973), 607-636. [7] J. Fletcher, On the conditional relationship between beta and return in international stock markets, International Review of Financial Analysis, 9, (2000), 235-245. [8] A. Gonzalez, T. Teräsvirta and D. van Dijk, Panel Smooth Transition Regression Model and an Application to Investment under Credit Constraint, NBER Working Paper, (2004). [9] A. Gonzalez, T. Teräsvirta and D. van Dijk, Panel Smooth Transition Regression Models, NBER Working Paper, (2005). [10] G.W.J. Granger and T. Teräsvirta, Modelling Nonlinear Economic Relationships, Oxford University, 1993. [11] B.E. Hansen, Threshold effects in non-dynamic panels: Estimation, testing and inference, Journal of Econometrics, 93, (1999), 345-368. [12] K.S. Im, M.H. Pesaran and Y. Shin, Testing for Unit Roots in Heterogeneous Panels, Journal of Econometrics, 115, (2003), 53-74. [13] A. Levin and C. J. Lin, Unit Root Tests in Panel Data: Asymptotic and Finite Sample Properties, Discussion Paper, University of California, San Diego, (1992). [14] A. Levin and C.J. Lin, Unit Root Tests in Panel Data: New Results, Discussion Paper, University of California, San Diego, (1993). [15] A. Levin, C. Lin and C.J. Chu, Unit Root Tests in Panel Data: Asymptotic and Finite-Sample Properties, Journal of Econometrics, 108, (2002), 1-24. [16] M. Nandha and S. Hammoudeh, Systematic risk, and oil price and exchange rate sensitivities in Asia-Pacific stock markets, Research in International Business and Finance, 21, (2007), 326-341. [17] K.P. Narayan and S. Narayan, Modeling the impact of oil prices on Vietnam’s stock prices, Applied Energy, 87, (2010), 356-361. [18] C.C. Nieh, The effect of the Asian financial crisis on the relationships among open macroeconomic factors for Asian countries, Applied Economics, 34, (2002), 491-502. 192 Threshold effects in the capital asset pricing model using PSTR... [19] G.N. Pettengill, S. Sundaram and I. Mathur, The conditional relation between beta and returns, Journal of Financial and Quantitative Analysis, 30, (1995), 101-116. [20] S.B. Ramos and H. Veiga, Risk factors in oil and gas industry returns: International evidence, Energy Economics, 33, (2011), 525-542. [21] G.Y.N. Tang and W.C. Shum, The conditional relationship between beta and returns: Recent evidence from international stock markets, International Business Review, 12, (2003), 109-126. [22] G. Woodward and R. Brooks, Do realized betas exhibit up/down market tendencies, International Review of Economics and Finance, 18, (2009), 511-519. [23] G. Woodward, and V. Marisetty, Introducing non-linear dynamics to the two-regime market model: Evidence, The Quarterly Review of Economics and Finance, 45, (2005), 559-581.