We undertake a comprehensive investigation of price and volume co-movement using daily New York Stock Exchange data from 1928 to 1987. We adjust the data to take into account well-known calendar effects and long-run trends. To describe the process, we use a seminonparametric estimate of the joint density of current price change and volume conditional on past price changes and volume. Four empirical regularities are found: (i) positive correlation between conditional volatility and volume; (ii) large price movements are followed by high volume; (iii) conditioning on lagged volume substantially attenuates the “leverage” effect; and (iv) after conditioning on lagged volume, there is a positive risk-return relation.

Productive factors such as human and phyaical capital are accumulated and trade can affect the steady-state levels of such factors. Consequently, trade liberalization will have dynamic effects on output and welfare as the economy moves to its new steady state, in addition to its usual static effects. The output impact of this dynamic effect is measurable and appears to be quite large. The welfare impact of this dynamic effect is also measurable. The size of this dynamic gain from trade depends on the importance of external scale economies.