First, he points out that the scoring drop has almost entirely occurred on the AL side; something I didn't know.
Interestingly, not all of baseball is suffering from fewer runs: the decline has been limited almost completely to baseball’s American League. AL teams are scoring .37 fewer runs per game, from 4.82 to 4.45; National League teams, meanwhile, have only reduced their scoring by .04 runs. Of the drop of 1,105 runs in the major leagues from last year, the American League has been responsible for a whopping 823 of those.
Then, he does on to draw correlations that he feels suggest that improvements on defense actually contributed to the offensive swing (not pitching).
If you find this to be tl;dr, here's the conclusion:
It’s not crazy to blame the scoring drought on fielding improvements: great fielders often contribute doubly to reduced scoring rates in their second role as below-average hitters. The 2010 Mariners are a good example: they added defensive tools in the off-season and continued to be one of the better fielding teams in the league this year, but their offense fell from the worst in the league in 2009 to one of the worst of all time in 2010. So when you’re putting a great fielder in your lineup, you’re also usually hurting your own offensive production, effectively reducing overall scoring on both sides of the ball.
Hayes Davenport, who provided research for the “Year of the Glove” segment on “Marketplace,” is a staff writer for Comedy Central’s “Big Lake” and “The Nick Swardson Sketch Show.” He is a certified stathead: his senior thesis at Harvard (from which he graduated in 2009) was called “Anti-Rationalist Rhetoric in American Baseball Journalism.