Jacob Luft of SI.com explores Andrew Zimbalist's theory that more records are being set in baseball now not because of PED's, but rather from a compression of talent in the major leagues.
Zimbalist's take is that as the number of major league jobs remains constant and the available talent pool grows, the harder it becomes for individual players to stand out above the rest. Conversely, increasing the number of major league jobs (via expansion) creates disparity in the talent pool and allows for record-breaking performance to happen again.
"Why, until 1998, were almost all of baseball's personal achievement records set between 1910 and 1930?" Zimbalist writes in May The Best Team Win: Baseball Economics and Public Policy. "Rogers Hornsby batted .424 in 1924, Hack Wilson knocked in 190 runs in 1930, Earl Webb whacked 67 doubles in 1931, Babe Ruth scored 177 runs in 1921 ... Baseball's stats are the product of competing forces and reveal little about the absolute quality of the players."