  The present paper proposes a new framework for describing the stock price
dynamics. In the traditional geometric Brownian motion model and its variants,
volatility plays a vital role. The modern studies of asset pricing expand
around volatility, trying to improve the understanding of it and remove the gap
between the theory and market data. Unlike this, we propose to replace
volatility with trading volume in stock pricing models. This pricing strategy
is based on two hypotheses: a price-volume relation with an idea borrowed from
fluid flows and a white-noise hypothesis for the price rate of change (ROC)
that is verified via statistic testing on actual market data. The new framework
can be easily adopted to local volume and stochastic volume models for the
option pricing problem, which will point out a new possible direction for this
central problem in quantitative finance.
