Posted By:
cmokingI'm not exactly sure what it is you don't understand...and I'm not 100% sure I am interpreting Gould's data correctly, so forgive me if the following sounds like the blind leading the blind 
Keep in mind too that I'm not 100% convinced about his numbers and I wonder how they would look if it was performed with more data and with other stats (see later in my post).
The average player over history has gotten better. Take aside expansion which throws a bit of a wrench in things (Maris in 1961 was, some argue, due to expansion and his facing weaker pitchers).
This means the best of the best are playing against better and better players as the timeline goes along. While the best of the best is not getting better or worse, the average player is getting better (this is what I think Gould is saying). So the top is static while the other players are getting better. If stats are perfectly smooth, maybe you would expect something like this where the top hitters hit 420 in the first decade, 410 in the second decade, 400 in the third, 390 in the fourth, 385 in the fifth, 380 in the sixth, etc. So that would mean fewer 400 hitters now than in the past.
But the fact that a few guys have been close (Brett in 1980 was .390, Gwynn was .394 in 1994), shows that it could have been 'easily' possible for one of those guys to actually have done it...it just turned out they didn't. .400 is an arbitrary line that we draw because it is a nice round number, we could have easily drawn the line at .390 instead.
I'll say this about Gould's argument though: it seems to me the best way to attack what his thoughts are is looking at OBP, and SLG rather than AVG. I haven't seen any stats, but I would suspect that SLG does not follow the same line as AVG. In the 20s and 30s maybe they would have been at an all time high, but I think they would have dipped down and then come back up in the 90s and 00s - especially with guys like Bonds and McGwire. That's why I'm not 100% convinced by his argument - but I don't have the ability to perform similar analysis for the other stats. Also, Gould stops in the 1970s, I wonder exactly what the numbers would have been if he also had the 80s, 90s and 00s in there. With guys like Boggs and Gwynn in those years, maybe that would have changed.