A friend of mine named Manish Malhotra just had an article published in Advisor Perspective in which I contributed. The concept is based on the fact that most wealth accumulation models assume a "random walk" sequence of returns, however, the direction of the market the previous year has an impact on the subsequent year (Bayesian probability). This fact should be included in the forecast of long-term wealth accumulation. This is a critical flaw in many wealth forecasting software packages and, quite honestly, causes them to give very wrong results. Check out the article on the Advisor Perspective website.