There's a chick (I say chick) she's probably 85 years old) on StockCharts.com called Joanne from Canada, and she maintains a whole system of statistical and technical analysis stuff called Above the Green Line. It's a momentum trading thing. She says everything reverts to the 250-day moving average, which she calls the Green Line. She's right, but sometimes that's because the Green Line eventually moves. In other words, things revert to the mean, but the mean also reverts to the thing at some level.