A Raging Bull or a Long-term Speculative Bubble? The Puzzling Case of the Karachi Stock Exchange

The objective of the study is to examine possible presence of nonlinear speculative bubbles in the Karachi Stock Exchange (KSE). Bubbles are argued to exist when there are substantial deviations of market value from the estimated fundamental values. We estimate a series of fundamental values from a four variable Vector Autoregression Model (VAR) using the main KSE100 index along with measures of world stock prices, the Pakistani exchange rate, and the Pakistani short-term interest rate. Residuals of this estimated fundamental time series are then tested for possible speculative deviations using a Hamilton regime switching test and a rescaled range Hurst coefficient test, with a further test for nonlinearity beyond the ARCH effects using the BDS statistic. For all of these, we reject the null hypotheses of the absence of speculative bubbles and nonlinearities beyond ARCH in these series. While these results suggest the possible presence of such bubbles, we note methodological limits on proving that due to the problem of mis-specified fundamentals. We further discuss some characteristics of the regulatory environment that may make it especially susceptible to such phenomena and may be considered by the policy-makers for the attenuation of speculative and manipulative behaviour.