Code:
YEAR NL REPLAY AL REPLAY
2007 1643 1564 (-79) 1354 1221 (-133)
2006 1515 1530 (+15) 1252 1322 (+70)
2005 1349 1322 (-22) 1216 1190 (-26)
2004 1336 1309 (-27) 1253 1225 (-28)
2003 1294 1181 (-113) 1279 1198 (-81)
2002 1514 1376 (-138) 1236 1168 (-68)
2001 1456 1845 (+389) 1647 1585 (-62)
2000 1627 1658 (+31) 1297 1082 (-215)
1999 1959 1896 (-63) 1462 1536 (+74)
1998 1609 1760 (+151) 1675 1382 (-293)
Well, here's a quick comparison of leagues through the most recent 10 year span...draw from it what you will, but in this decade, it seems that the AL is down overall, while the NL is up overall. As you can see, some years the numbers are really very close, with only a couple of really out of whack variances (+389 and -293).
Again, this is using the default setup right out the box, so to speak. I'm still compiling numbers, but this is what I've got so far