Financial factor influence on scaling and memory of trading volume in stock market

We study the daily trading volume volatility of 17,197 stocks in the U.S. stock markets during the period 1989--2008 and analyze the time return intervals $τ$ between volume volatilities above a given threshold q. For different thresholds q, the probability density function P_q(τ) scales with mean interval <τ> as P_q(τ)=<τ>^{-1}f(τ/<τ>) and the tails of the scaling function can be well approximated by a power-law f(x)~x^{-γ}. We also study the relation between the form of the distribution functi...