Expiration-Day Effects of Stock and Index Futures and Options in Sweden: The Return of the Witches

摘要

Recently, the NASDAQ-OMX Nordic Exchange announced a change of expiration day for the OMXS 30 index futures and options. The OMXS 30 index derivatives used to expire on the fourth Friday of the expiry month while derivatives on individual stocks expired on the third Friday. After the change, derivatives on both the index and individual stocks expire on the third Friday of the expiry month making the third Friday the "quadruple witching Friday" as stock futures, stock options, index futures, and index options expire simultaneously. This contractual change provides a unique opportunity to investigate its impact on expiration-day effects. The results show that there is hardly any expiration-day effect due to the derivatives' expirations before or after the contractual change, except the abnormally higher trading volumes at the stock derivatives' expirations before the change, and on the quadruple witching Fridays after the change. Most importantly, there is no significantly intensified abnormal volume, volatility, or price distortion effect due to the seemingly "extraordinary" change in the OMXS 30 index derivatives, despite the quadruple witching expirations after the change.