This study considers the joint influence of contemporaneous and lagged responses to macroeconomic news in explaining US day-of-the-week effects. Macroeconomic news is measured by movements in large firms' stock prices. The average response of smaller stocks to these movements is abnormally high on Mondays, especially in down markets. After corrections for these asymmetries, the US day-of-the-week effect weakens substantially for most size-ranked portfolios in most of the six approximately equal subperiods between 1962 and 1992. These findings suggest that seasonals in processing macroeconomic news account for much of the day-of-the-week effect in equity returns.

Abstract A three parameter stochastic process, termed the variance gamma process, that generalizes Brownian motion is developed as a model for the dynamics of log stock prices. Theprocess is obtained by evaluating Brownian motion with drift at a random time given by a gamma process. The two additional parameters are the drift of the Brownian motion and the volatility of the time change. These additional parameters provide control over the skewness and kurtosis of the return distribution. Closed forms are obtained for the return density and the prices of European options.The statistical and risk neutral densities are estimated for data on the S&P500 Index and the prices of options on this Index. It is observed that the statistical density is symmetric with some kurtosis, while the risk neutral density is negatively skewed with a larger kurtosis. The additional parameters also correct for pricing biases of the Black Scholes model that is a parametric special case of the option pricing model developed here.