Options and Market Efficiency

I use five separate measures of deviation from Put-Call Parity of options on a stock without splits or dividends as separate negative measures for efficiency of the market ecosystem consisting of the underlying stock derivatives and risk-free securities. I develop a theory of trading volume as a function of short sales costs dispersion of investor valuations float and transaction costs and that of market efficiency as a function of trading volume and number of analysts covering the stock. I use Three-Stage Least Squares (3SLS) to estimate this structural system separately for Nasdaq and non-Nasdaq U.S. stocks over 1996-2015. I find contrary to much previous theoretical and empirical work that the impact of short sales costs & constraints on market efficiency is not significantly negative and that the impact of trading volume on market efficiency is not significantly positive.