If a baseball player hits well early in the season, will he do just as well later on?
Halfway through the 2005 baseball season, John Olerud was having a great year with the Boston Red Sox. His batting average was .405, far better than that of most players. If someone had offered to wager with you on what his batting average would be for the rest of the season, what would you have bet?
It might seem like .405 would make sense, the same as the first half of the season. But if that had been your choice, you wouldn't have done so well. In the second half of the season, Olerud's batting average was down to .257. And if you'd used that method to bet on Henry Blanco of the Chicago Cubs, who had a first-half-season batting average of .151, you would have lost money too: in the second half of the season, his average was .305. Aaron Hill of the Toronto Blue Jays went from .359 to .226. And the list goes on.
In fact, according to a new analysis by