Seems like day games and night games don't matter much anymore. And from a stat standpoint, this is probably true. Overall, there is very little difference in offensive production based on whether games are played in daylight or under artificial light.
Of course the data is available at BB-Ref, it's just that you have to go digging for it on a year-by-year basis.
|Gio Gonzalez: no Dracula on the slab...|
Now, the A's weren't very good at all in day games the year before...but their pitching staff developed a good bit last season and there's a reasonable possibility that they will hold most of the level of performance they achieved in 2010. You have to hand it to them, they keep turning up arms--last year, they looked as though they scored a coup with 30-year old left-hander Bobby Cramer, a 38th round draft pick (Mariners) in 2001, derailed by Tommy John surgery the next year, out of the game for two years. (You can read an excellent interview with him--a two-parter--at the Athletics Nation blog. The interview points up a fact that's often overlooked about the A's, given their Moneyball aura--they have a good scouting network and have done a good job of raiding other organizations for scouting personnel.)
I wonder about that odd spike in 1952: someone ought to double-check that data. Otherwise, this has been a rather classic ramp-up to a steady state of affairs.
There is a bit of variation in the number of day games being played in MLB: the Cubs still play the most (78 in 2010), while the Marlins (42), Red Sox (43), and Dodgers (44) had the fewest day games. (The A's were in the middle of the pack in 2010, with 56 day games.) So the effective range for day games within the aggregate is 26% to 46%; flipping those figures to match the chart, that's 54% to 74% played under the lights.
By Thursday, night games will once again prove to be the majority of major league contests, and they won't be going back. We'll keep an eye on day game won-loss records periodically during the year, and maybe we'll even synthesize some of the historical results. Maybe...