“Expiration hour effect of futures and options markets on stock market” — A case study on NSE (National Stock Exchange of India)

This paper studies the effect of expiration day of the Index futures and Options on the trading volume, variance and price of the underlying shares. The impact of derivatives trading on the underlying stock market has been widely documented in the Finance literature. In particular, significant differences in the statistical properties of asset returns (for instance, mean and variance) during expiration and non-expiration days have been advanced as an evidence for the destabilization effect (or lack there of) of derivative instruments. The earlier studies have, however, drawn their conclusions without rigorously modelling the underlying stochastic data generation process. Given that the statistical properties mentioned before are merely traits of the asset returns, this approach can lead to spurious results if analyzed in isolation of the underlying process. We propose to address this crucial shortcoming by examining the expiration day effect from a GARCH (Generalized Auto Regressive Conditional Heteroskedastic) framework. We use both daily and high frequency (5 min and 10 min) data on S&P CNX Nifty Index. Our central finding using intra-day data is that while there is no pressure – downward or upward – on index returns, the volatility is indeed significantly affected by the expiration of contracts. This effect, however, doesn’t show up in daily data.