National League Power Outage?

After browsing over some statistics from baseballreference.com from previous seasons I quickly noticed one trend, offense in the National League is becoming increasingly valuable. It's no secret that the crackdown on steroids and performance enhancers in baseball have shifted the advantage back toward the pitchers, as the following illustrations will indicate, but it is a little surprising how gradual and constant the change has been. This graph represents the average runs scored per game in all National League contests since 2006: This graph represents the average number of homers in all National League games since 2006: Furthermore, the league has also seen progressive decreases in the last six seasons on a per-game basis in hits, batting average, on-base percentage, slugging, OPS, total bases and hit batsman. Not surprisingly the ERA over this time span has decreased as well. It went from being 4.49 in 2006 to 3.82 in 2011. Pitchers are allowing fewer wal...