K/BB ratio split by league
Posted by Andy on June 23, 2010
Here is a look at all-time K/9 and BB/9 rates broken out in the NL vs. the AL.
Yesterday I posted a graph showing K/9 IP, BB/9 IP, and K/BB ratio across all of baseball each year since 1901. Here is the same data, split by league.
Some of this is quite surprising. Here are my observations:
- The NL has been striking out more batters than the AL for a long time. Yes, the difference has been larger since the introduction of the DH in 1973 but the NL has been ahead tied or ahead every year since 1969 and most years since 1948. Thoughts on why this was?
- I noted yesterday that walks and strikeouts were nearly identical for the entire period 1920-1950 but this graph shows it wasn't quite so simple. The AL and NL were very similar in strikeouts through that period, but the AL walked more batters than it struck out (yielding a K/BB ratio a little bit under 1.0) while the NL struck out more than it walked (yielding a K/BB ratio a little bit above 1.0.) It's weird how the effects quite nearly cancel each other out since they were independent events happening in separate leagues with no interleague play.
- During the Steroids Era 1993-2006 there was quite a large disparity in strikeout rates that mirrors the increased run-scoring in the AL as compared to the NL. That difference has shrunken quite a bit in the last few years and both leagues have nearly exactly a 2.0 K/BB ratio with a few more of each in the NL than in the AL.
June 23rd, 2010 at 9:41 am
The little edge the NL had in strikeouts around 1960 is the Dodgers. They were getting about 300 over the league average. Great staff, nasty lighting.
June 23rd, 2010 at 10:23 am
Oh this is fascinating. Just lookin', I'm thinking about all the great strikeout pithers in the 60's & 70's, who were NL'ers most of that time, like Bob Gibson, Don Sutton, Steve Carlton, and Tom Seaver. The ones that come to mind from the AL are Bert Blyleven and Mickey Lolich. Of course, Nolan Ryan played in both leagues and put up numbers wherever he was.
But doin' a quick play index search for most K's by league from 1964-1989, I find...
15 NL pitchers with 1500+ K's
15 AL pitchers with 1500+ K's (Ryan's on both lists)
...it wasn't like the dominating guys were mostly in the NL. It must be a general difference in how each league felt they should build teams. I remember when I was growing up in the early/mid 80's, the general feeling was that the NL was a pitching & defense league while the AL was an offensive league.
June 23rd, 2010 at 5:31 pm
For a while the AL and NL umpires had different uniforms -- one wore a chest protector outside the jacket, the other inside, and this may have affected their stance and thus their strike zones. That lasted longer than just the late 40s/early 50s however, so I'm not sure why there was such a discrepancy at that time. It's not just the player populations. Apparently in World Series games of that era, there were more walks when AL umpires handled home plate than with NL umps.