The WSJ has an article on the decline of Major League Baseball’s National League in recent decades. Unlike Gibbons or Will, the author is quite straightforward:

The plight of the NL seems rooted in a chain of events that began in 1973 when the AL adopted the designated-hitter rule — which allows for the pitchers to be replaced in the batting order by a full-time hitter who doesn’t play in the field. The disparity was spurred by new ballpark construction; an unprecedented crop of young power hitters who, for various reasons, almost all fell to the AL; a series of disastrous trades and free-agent signings by NL teams; and a tradition of innovation in the AL that began in the mid-1990s with the Oakland As.

Interesting, though NL partisans (coughNies) will continue to b*tch and moan about purity, despite how little it has to do with the above conversation.