Regime-Dependent Relationships Between the Implied Volatility Index and Stock Market Index

We examine regime-dependent dynamics between Korea's representative implied volatility index (VKOSPI) and stock market index (KOSPI 200) using a two-regime threshold vector error correction model (TVECM). By analyzing high-quality daily data from January 2003 to June 2013, we make the following interesting observations based on a model with regime splitting. First, regardless of regime, we observe a negative contemporaneous correlation between the VKOSPI and KOSPI 200. Second, while the KOSPI 200 generally leads the VKOSPI under normal market conditions (lower regime), this relationship is overturned when market volatility measured by the VKOSPI level is extremely high (upper regime). Third, in the TVECM framework, the effects of lagged VKOSPI on the KOSPI 200 are positive only in the upper regime, while the effects of lagged KOSPI 200 on the VKOSPI are positive only in the lower regime; this cannot be explained by the traditional framework of an asymmetric volatility phenomenon. Fourth, the KOSPI 200 exhibits greater sensitivity to implied volatility shocks in the upper regime than it does to those in the lower regime.