Long-term Memory in Stock Market Prices

A test for long-term memory that is robust to short-range dependence is developed. It is a modification of the R/S statistic, and the relevant asymptotic sampling theory is derived via functional central limit theory. Contrary to previous findings, when applied to daily and monthly stock returns indexes over several time periods this test yields no evidence of long-range dependence once short-range dependence is accounted for. Monte Carlo experiments show that the modified R/S test has power against at least two specific models of long-term memory, suggesting that models with short-range dependence may adequately capture the behavior of historical stock returns. Copyright 1991 by The Econometric Society.