The best stock-timing system of the 1980s and 1990s is still beating the market

One of the best short-term market timing systems of the 1980s and 1990s was given up for dead some years ago, but it’s started beating the market again.

The Seasonality Timing System, created in the 1970s by Norman Fosback, then head of the Institute for Econometric Research, is simple and mechanical. It says to invest in stocks around the turn of the month and immediately prior to stock-exchange holidays — and shelter in a money-market fund at all other times.

Fosback…