Pattern Of Short-Term Volatility Accentuation Within The Trading Day: An Investigation Of The U.S. And European Equity Markets

Deniz Ozenbas, Montclair State University


Trading friction leads into accentuated stock price volatility over the short term. As such, short-term accentuated volatility can be viewed as symptomatic of a market with increased inefficiencies in the price discovery process. If price discovery is marked by price swings, runs and reversals, then short period (intra-day) volatility is heightened in that market. In this study, we use return series with various differencing intervals that are as short as half-hour and as long as two weeks to investigate the short-term volatility accentuation in five different equity markets: the Nasdaq Stock Market and the New York Stock Exchange in the US, and the London Stock Exchange, Deutsche Boerse and Euronext Paris in Europe. In all these markets, we investigate the individual stocks that make up a major index during the calendar year 2000. Variance-ratio statistics are employed to investigate the quality of these five markets. Results confirm an intra-day reverse J-shaped pattern of half-hour volatility in these markets. The evidence also suggests an accentuation of volatility during longer periods, such as 24-hour intervals. This accentuation appears to subside when we extend our differencing interval to longer periods such as one-week or two-week returns.