A number of studies on the S&P 500 index options market claim that the no arbitrage assumption cannot be rejected for this market because either the martingale restriction defined in Longstaff (1995) cannot be rejected by the data, or, even when it is rejected, a large proportion of the...

We study options market participants’ trading behavior before and after the options multiplier increases. After the options multiplier increases, the options market becomes more efficient. By analyzing the high-frequency microstructure dataset, we show that local retail and local institutional...