At the end of May, the American League led 62 games to 58. From that point until the end of July, they've won 54 of 96 games (a .563 WPCT) in their interleague matchups.
One thing to keep in mind, however--and there has been a strong tendency in the sabe press to overlook this fact--is that the schedule strength in the random yearly matchups has not been equal for both leagues.
This year is no exception.
Thus far, the NL has played 24 more games against winning AL teams than vice versa.
That may not sound like much, but in the context of interleague play (217 contests thus far through 8/1), the AL has played only 41% of its games against winning NL teams.
The NL team that's getting killed the most in interleague games thus far in 2013: the Colorado Rockies (3-12). Nine of those games have come against winning teams; they're 2-7 in those games. They had the misfortune of having games scheduled against Toronto in June--just when the Blue Jays were in the midst of their 11-game winning streak.
Thanks to Forman et fil (and we do try to thank them as often as possible...) we can now capture statistical summaries for interleague play. We'll be running those leaderboards here soon, since we can't resist such recondite research.
The oddity in this year's data comes explicitly from the scheduling changes implemented for interleague play in 2013. It was highly unlikely in previous years that hitters could wind up playing more than 18 interleague games in a season, mostly due to the placement of the games in a highly concentrated part of the schedule.
Not so this year. Alfonso Soriano played in 20 interleague games for the Cubs--their entire interleague schedule for 2013--prior to his trade to the Yankees last week. He's already played in two more as the Yankees make a West Coast swing that features interleague contests against the Dodgers and the Padres.
It's possible that Soriano (who leads in opposite-league HRs thus far this year, with seven...) will play in as many as 28 interleague games in 2013.
The August schedule is interesting largely due to the fact that the three teams closest to each other in the AL East will each spend a hefty slice of the month playing National League teams.