Blacks in baseball: the peak was 20%, not 27%
Remember that statistic that said that the percentage of (American) blacks in major league baseball hit a high of 27% back in the early 1970s? It turns out that isn't true.
According to Carl Bialik, of the Wall Street Journal, the 27% figure applied only to
full-time non-pitchers non-pitchers with at least 50 games that season. If you include everyone, the actual high was 20%.
Today's figure is around 8%, so there's still a sizeable drop to explain – just not as large as originally purported.
The originator of the original "27%" figure, John Loy, used it in a study where he looked for evidence of "stacking" (which means restricting black players to certain positions). He found that African-American players were disproportionally represented in the outfield, and suggested that teams put blacks in the outfield because that way they'll have less interaction with their (mostly white) teammates.
But didn't Bill James note (maybe in his 1987 rookie study?) that black players appeared to keep their foot speed a lot longer than white players did? I remember he once mentioned that Rick Monday was drafted partially because he was so fast. Today, of course, Monday isn't associated with speed at all – he's remembered mostly in connection with flag burning and breaking Tango's heart.
Anyway, if Bill was right, that would certainly explain the effect – you have to be reasonably fast to play the outfield, but not to catch, play first base, or designated hit. So there would appear to be some segregation by race, when it's really by speed.
I haven't read the Loy study – he might have corrected for this. I'm just saying.
There's another effect Bialik mentions:
" ... other research suggests that latent racism within the game tended to reserve bench spots for white players."
"[SABR's Mark] Armour found that black players consistently have outperformed their contemporaries in total "win shares," a statistic developed by baseball numbers pioneer Bill James that represents players' total contribution to a team's success. ... One reason black players were, on average, better than white players was that they needed to be to make the roster."
I think Bill James debunked this one a long time ago too. If blacks are slightly better than whites, on average, the effect is magnified at the extremes of ability.
Suppose that, on average, whites average 100 "points" of ability, but blacks average 103. And suppose both races are normally distributed with standard deviation of 10. Finally, let's say blacks are 15% of the population.
In that case, about 24% of blacks will be at 110 or higher – but only 16% of whites. In terms of population, 21% of the 110+ players will be black.
But now, let's look at the star players, the ones above 130. Only 0.35% of blacks will achieve this mark. But for whites, it's a lot less -- 0.13%. So in that group, almost 40% of players will be black.
-- 40% black players at 130+ (stars)
-- 21% black players at 110+ (bench players)
So there's a very plausible explanation of why there are proportionally fewer blacks on the bench, than there are blacks playing full time.
Again, I'm not sure what specific studies Bialik is referring to, but I hope there's more evidence for the racism hypothesis than just the numbers he mentions.
Hat Tip: Bob Timmermann