The Effect of Long Term Dependence on Risk-Return Models of Common Stocks

In a previous paper the authors have shown that common stock returns are characterized by a phenomenon called long term dependence. The present paper discusses the implications of the presence of long term dependence for existing risk-return models in finance. Specifically, it is shown that (1) risk rankings of stocks or portfolios tend to vary with the differencing interval chosen to measure security returns, (2) efficient portfolios vary with the differencing interval selected, and (3) the unrealistic, homogeneous time horizon assumption of the capital asset pricing model must be retained in order for the model to hold.