Testing the Efficient Market Hypothesis in Borsa Istanbul Sub-Indices: Evidence from Unit Root Tests with Fourier Breaks and Non-Linearity

Abstract

The aim of this study is to test the validity of the efficient market hypothesis for six indexes (XU100, XTUMY, XUHIZ, XUMAL, XUSIN, XUTEK) in BIST. For this, ADF, RALS-ADF, Fourier-ADF and Fourier-KSS unit root tests were used. The longest period was used for each index in terms of data availability as the analysis period. Unlike the literature, the validity of the efficient market hypothesis for six indices in the BIST has been comprehensively and comparatively examined by considering both structural breaks, non-normal distribution and non-linearity at the same time. According to the empirical findings, the null hypothesis could not be rejected in all unit root tests applied in the XUHIZ index. In other words, strong evidence has been obtained for the XUHIZ index in line with the effective market hypothesis. On the contrary, as a result of all unit root tests applied in the XUMAL index, the null hypothesis was rejected and the results indicating that the efficient market hypothesis was invalid were obtained. In other indices, it was observed that considering structural breaks and nonlinearity caused differences in the results. This situation highlights the importance of choosing the appropriate test for the data set. 

Keywords

• Efficient Markets Hypothesis
• Unit Root Tests
• Borsa Istanbul

Borsa İstanbul Alt Endekslerinde Etkin Piyasa Hipotezinin Test Edilmesi: Fourier Kırılmalı ve Doğrusal Olmayan Birim Kök Testlerinden Kanıtlar

Abstract

Bu çalışmanın amacı Borsa İstanbul’da (BİST) yer alan altı endeks için (XU100, XTUMY, XUHIZ, XUMAL, XUSIN, XUTEK) etkin piyasa hipotezinin (EPH) geçerliliğini test etmektir. Bunun için ADF, RALS-ADF, Fourier-ADF ve Fourier-KSS birim kök testlerinden yararlanılmıştır. Analiz dönemi olarak veri bulunabilirliği açısından her bir endeks için en uzun dönem kullanılmıştır. Literatürden farklı olarak BİST’de yer alan altı endeks için EPH’nin geçerliliği aynı anda hem yapısal kırılmalar hem normal dağılmama durumu hem de doğrusal olmama durumu dikkate alınarak kapsamlı ve karşılaştırmalı bir şekilde incelenmiştir. Elde edilen ampirik bulgulara göre XUHIZ endeksinde uygulanan tüm birim kök testlerinde boş hipotez reddedilememiştir. Yani XUHIZ endeksi için etkin piyasa hipotezi geçerli doğrultusunda güçlü kanıtlar elde edilmiştir. Aksine XUMAL endeksinde ise uygulanan bütün birim kök testleri sonucunda boş hipotez reddedilerek etkin piyasa hipotezinin geçersiz olduğuna yönelik sonuçlar elde edilmiştir. Diğer endekslerde ise yapısal kırılmaların ve doğrusal olmama durumunun dikkate alınmasının sonuçlar üzerinde farklılıklara neden olduğu gözlemlenmiştir. Bu durum da veri setine uygun test seçiminin önemini öne çıkarmaktadır. 

Keywords

• Etkin Piyasalar Hipotezi
• Birim Kök Testleri
• Borsa İstanbul

References

1. Akgun, A. and Sahin, I. (2017). The testing of efficient market hypothesis in Borsa Istanbul. Annals Constantin Brancusi University of Targu Jiu, Letters & Social Sciences Series, 2, 35-48. Retrieved from https://heinonline.org/
2. Alexeev, V. and Tapon, F. (2011). Testing weak form efficiency on the Toronto Stock Exchange. Journal of Empirical Finance, 18(4), 661-691. https://doi.org/10.1016/j.jempfin.2011.05.002
3. Aliyev, F. (2019). Testing market efficiency with nonlinear methods: Evidence from Borsa Istanbul. International Journal of Financial Studies, 7(2), 27-37. https://doi.org/10.3390/ijfs7020027
4. Altuntaş, M. (2021). The interest rate parity in fragile five countries: Evidence from unit root tests with breaks. Journal of Economic Policy Researches, 8(2), 327-349. Retrieved from https://dergipark.org.tr/en/pub/iuipad
5. Balke, N.S. and Fomby, T.B. (1997). Threshold cointegration. International Economic Review, 38(3), 627-645. https://doi.org/10.2307/2527284
6. Bektur, Ç. and Aydın, M. (2019). Borsa İstanbul ve alt endekslerinde zayıf formda piyasa etkinliğinin analizi: Fourier yaklaşımı. Akademik İncelemeler Dergisi, 14(2), 59-76. https://doi.org/10.17550/akademikincelemeler.556185
7. Broock, W.A., Scheinkman, J.A., Dechert, W.D. and LeBaron, B. (1996). A test for independence based on the correlation dimension. Econometric Reviews, 15(3), 197-235. https://doi.org/10.1080/07474939608800353
8. Chaudhuri, K. and Wu, Y. (2003). Randomwalk versus breaking trend in stock prices: Evidence from emerging markets. Journal of Banking & Finance, 27, 575–592. https://doi.org/10.1016/S0378-4266(01)00252-7

9. Christopoulos, D.K. and León-Ledesma, M.A. (2010). Smooth breaks and non-linear mean reversion: Post-Bretton Woods real exchange rates. Journal of International Money and Finance, 29(6), 1076-1093. https://doi.org/10.1016/j.jimonfin.2010.02.003
10. Coşkun, Y. and Seven, U. (2016). Efficiency of financial markets. In A. Gündoğdu (Ed.), Financial markets and institutions: Theory and practice in Turkey (289-319). Ankara: Seckin Publishing.
11. Çevik, E.İ. (2018). Borsa İstanbul zayıf formda etkin mi? Markov-Switching ADF testi yaklaşımı. BDDK Bankacılık ve Finansal Piyasalar Dergisi, 12(2), 9-30. Erişim adresi: https://dergipark.org.tr/en/pub/bddkdergisi/
12. Dickey, D.A. and Fuller, W.A. (1979). Distribution of the estimators for autoregressive time series with a unit root. Journal of the American Statistical Association, 74(366a), 427-431. https://doi.org/10.1080/01621459.1979.10482531
13. Enders, W. and Lee, J. (2012). A unit root test using a Fourier series to approximate smooth breaks. Oxford Bulletin of Economics and Statistics, 74(4), 574-599. https://doi.org/10.1111/j.1468-0084.2011.00662.x
14. Eyüboğlu, K. ve Eyüboğlu, S. (2020). Borsa İstanbul sektör endekslerinin etkinliğinin Fourier birim kök testleri ile analizi. Uluslararası İktisadi ve İdari İncelemeler Dergisi, 29, 23-44. https://doi.org/10.18092/ulikidince.648896
15. Fama, E.F. (1970). Session topic: Stock market price behavior. The Journal of Finance, 25(2), 383-417. https://doi.org/10.2307/2325486
16. Gozbasi, O., Kucukkaplan, I. and Nazlioglu, S. (2014). Re-examining the Turkish stock market efficiency: Evidence from nonlinear unit root tests. Economic Modelling, 38, 381-384. https://doi.org/10.1016/j.econmod.2014.01.021
17. Hansen, B.E. (1995). Rethinking the univariate approach to unit root testing: Using covariates to increase power. Econometric Theory, 11(5), 1148-1171. Retrieved from https://www.cambridge.org/
18. Harvey, D.I., Leybourne, S.J. and Xiao, B. (2008). A powerful test for linearity when the order of integration is unknown. Studies in Nonlinear Dynamics & Econometrics, 12(3). https://doi.org/10.2202/1558-3708.1582
19. Hasanov, M. (2009). Is South Korea's stock market efficient? Evidence from a nonlinear unit root test. Applied Economics Letters, 16(2), 163-167. https://doi.org/10.1080/13504850601018270
20. Hasanov, M. and Omay, T. (2008). Nonlinearities in emerging stock markets: Evidence from Europe's two largest emerging markets. Applied Economics, 40(20), 2645-2658. https://doi.org/10.1080/00036840600970310
21. Im, K.S. and Schmidt, P. (2008). More efficient estimation under non-normality when higher moments do not depend on the regressors, using residual augmented least squares. Journal of Econometrics, 144(1), 219-233. https://doi.org/10.1016/j.jeconom.2008.01.003
22. Jarque, C.M. and Bera, A.K. (1987). A test for normality of observations and regression residuals. International Statistical Review/Revue Internationale de Statistique, 55(2), 163-172. https://doi.org/10.2307/1403192
23. Kapetanios, G., Shin, Y. and Snell, A. (2003). Testing for a unit root in the nonlinear STAR framework. Journal of Econometrics, 112(2), 359-379. https://doi.org/10.1016/S0304-4076(02)00202-6
24. Kapusuzoglu, A. (2013). Testing weak form market efficiency on the Istanbul stock exchange (ISE). International Journal of Business Management and Economic Research, 4(2), 700-705. Retrieved from http://www.ijbmer.com/
25. Karademir, F. ve Evci, S. (2020). Borsa İstanbul’da zayıf formda piyasa etkinliğinin test edilmesi: Sektörel çerçevede bir analiz. Business & Management Studies: An International Journal, 8(1), 82-100. https://doi.org/10.15295/bmij.v8i1.1416
26. Kilic, Y. and Fatih, M.B. (2016). The efficient market hypothesis: Evidence from Turkey. International Journal of Academic Research in Business and Social Sciences, 6(10), 262-272. doi:10.6007/IJARBSS/
27. Kurtaran, A.T., Kurtaran, A. ve Çelik, M.K. (2018). Zayıf formda piyasa etkinliğinin Türkiye hisse senedi piyasasında test edilmesi. Uluslararası İktisadi ve İdari İncelemeler Dergisi, Özel sayı, 457-474. Erişim adresi: https://dergipark.org.tr/tr/pub/ulikidince/
28. Kwiatkowski, D., Phillips, P.C., Schmidt, P. and Shin, Y. (1992). Testing the null hypothesis of stationarity against the alternative of a unit root: How sure are we that economic time series have a unit root? Journal of Econometrics, 54(1-3), 159-178. https://doi.org/10.1016/0304-4076(92)90104-Y
29. Lee, J. and Strazicich, M.C. (2003). Minimum lagrange multiplier unit root test with two structural breaks. Review of Economics and Statistics, 85(4), 1082-1089. Retrieved from www.jstor.org
30. Narayan, P.K. (2005). Are the Australian and New Zealand stock prices nonlinear with a unit root? Applied Economics, 37, 2161–2166. https://doi.org/10.1080/00036840500217887
31. Narayan, P.K. (2008). Do shocks to G7 stock prices have a permanent effect? Evidence from panel unit root tests with structural change. Mathematics and Computers in Simulation, 77, 369–373. https://doi.org/10.1016/j.matcom.2007.03.003
32. Narayan, P.K. and Popp, S. (2010). A new unit root test with two structural breaks in level and slope at unknown time. Journal of Applied Statistics, 37(9), 1425-1438. https://doi.org/10.1080/026647 60903039883
33. Narayan, P.K. and Smyth, R. (2004). Is South Korea's stock market efficient? Applied Economics Letters, 11(11), 707-710. https://doi.org/10.1080/1350485042000236566
34. Omay, T. (2015). Fractional frequency flexible Fourier form to approximate smooth breaks in unit root testing. Economics Letters, 134, 123-126. https://doi.org/10.1016/j.econlet.2015.07.010
35. Onur, O. (2021). BİST-100 endeksinde doğrusal ve doğrusal olmayan yöntemlerle zayıf formda piyasa etkinliğinin testi. Mehmet Akif Ersoy Üniversitesi Uygulamalı Bilimler Dergisi, 5(1), 107-123. https://doi.org/10.31200/makuubd.884585
36. Ozdemir, Z.A. (2008). Efficient market hypothesis: evidence from a small open-economy. Applied Economics, 40(5), 633-641. https://doi.org/10.1080/00036840600722315
37. Perron, P. (1989). The great crash, the oil price shock, and the unit root hypothesis. Econometrica: Journal of the Econometric Society, 57(6), 1361-1401. https://doi.org/10.2307/1913712
38. Tuna, G. ve Öztürk, M. (2016). Piyasa etkinliğinin yapısal kırılmalı birim kök testleri ile incelenmesi: Türkiye pay senedi piyasası uygulaması. Uluslararası Yönetim İktisat ve İşletme Dergisi, 12(12), 548-559. Erişim adresi: https://dergipark.org.tr/en/pub/ijmeb/
39. Yücel, Ö. (2016). Finansal piyasa etkinliği: Borsa İstanbul üzerine bir uygulama. International Review of Economics and Management, 4(3), 107-123. https://doi.org/10.18825/irem.16916
40. Zeren, F., Kara, H. ve Arı, A. (2013). Piyasa etkinliği hipotezi: İMKB için ampirik bir analiz. Dumlupınar Üniversitesi Sosyal Bilimler Dergisi, 36, 141-148. https://dergipark.org.tr/en/pub/dpusbe/