We use the power law function to study changes in the distribution of trading volumes of S&P 500 stocks and non-S&P 500 stocks from 1960 to 2013. We find that the distribution of daily trading volumes has changed significantly for different baskets of non-index stocks and trading has become more...

We model the distribution of daily stock trading volume using the power law and document a new phenomenon. The power law exponent systematically increases with time suggesting that trading is becoming increasingly concentrated in a subset of stocks