The study accepts that VA will tend to outperform when there is mean reversion in market returns (e.g. a high return one month tends to be followed by a low return the following month). But even if an investor identifies a market which mean-reverts, VA is unlikely to be the best strategy to use. Consistent mean reversion would mean that market returns are easy to forecast, so it would be easy to construct other strategies which would take advantage of this predictability more effectively than VA. Mean reversion in the market is not the same concept as regression to the mean as used by statisticians where retesting a non-random sample of a population tends to produce results that are closer to the mean than the original test. The existence of mean reversion in financial markets is controversial and is a subject of active research. If it exists, then it is almost certainly very slight.