In this article the long memory and nonlinear properties of share prices in the UK's stock exchange and alternative investment markets are explored. The results suggest that the most commonly traded shares exhibit long memory. Thus, the validity of market efficiency is questioned.

In this paper the long memory and non-linear properties of share prices in the UK’s Stock Exchange and AIM are explored. The results suggest that the most commonly traded shares exhibit long memory thus raising interesting issues about the validity of normal assumptions of market efficiencies.