The behavior of intra-daily exchange rates

The behavior of exchange rates is examined as they evolve continuously over time. The data consist of Swiss franc/U.S. dollar rates for nine days during the years 1978–1980 as quoted by a major Swiss dealer operating on the interbank market. Since this market is highly organized, the observations are market prices at the same time. The distributions of relative changes in exchange rates measured over one minute are highly leptokurtic. The normal distribution is rather rapidly approached when the measurement interval is lengthened from one up to ten minutes. Time series analysis reveals that the natural logarithms of exchange rates are adequately described by a random walk, the same stochastic process as has been found for daily, weekly, monthly and quarterly observations. For short time intervals, significant autocorrelations sometimes occur at the first few lags, which are, however, not stable enough over time to form a basis for reliable forecasts.