Stock market structure and volatility

The procedure for opening stocks on the NYSE appears to affectprice volatility. An analytical framework for assessing themagnitude of the structurally induced volatility is presented.The ratio of variance of open-to-open returns to close-to-closereturns is shown to be consistently greater than one for NYSEcommon stocks during the period 1982 through 1986. The greatervolatility at the open is not attributable to the way in whichpublic information is released since both the open-to-open returnand the close-to-close return span the same period of time.Instead, the greater volatility appears to be attributable toprivate information revealed in trading and to temporary pricedeviations induced by specialist and other traders. The impliedcost of immediacy at the open is significantly higher than atthe close. Other empirical evidence in this article documentsthe volume of trading at the open, the time delays between theexchange opening and the first transaction in a stock, the differencein daytime volatility versus overnight volatility, and the extendto which volatility is related to trading volume.