The impact of net buying pressure on index options prices

This study examines whether the demand for options, as measured by the net buying pressure of index options, explains the implied volatility structure created by options prices. We decompose the buying pressure into the direction-motivated (i.e., delta-informed) and the volatility-motivated (i.e., vega-informed) demand for options. After controlling for options traders' hedging demand, we find that both delta- and vega-informed trading play significant roles in explaining changes in implied volatility. Foreign institutions are more directionally informed in index options trading than their domestic counterparts are. Domestic investors effectively implement volatility trading using put options.