Why do we have to "agree"?
We can look it up.
Since 1965, both the average MLB player and
NBA player have both gotten about 1" taller (I picked the NBA because they seem likely to have the absolute most pressure to select for height of anything).
I did. I can see you chose to link your data to years you had NFL data, but you missed the time period where the NBA players grew the most. Well I concede the premise height hurts hitters from the book seems false, the idea that other sports have had a bigger increase in size than baseball is not. But while the NFL and NBa seemed to flatten out, pitchers at least seem to continue getting taller.
This article says the average olineman has gone from 6-0 210 in the 20s to 6-5 310 today
http://www.businessinsider.com/nfl-50s-tim-tebow-would-have-been-an-offensive-lineman-2011-10?op=1
The NFL average is mostly due to running backs getting shorter since 1970, but few psotions have changed morew than an inch since 1970.
Nba players have gone from 6-4 in the 50s to 6-7 ever since 1980. (perhaps the 3 point line ended the advantage of increasingly bigger players, that was a stated goal of some proponents) Batter height stayed constant from 1950 to 1980 and even with the recent uptick has gone up only an inch in the time basketball increased 3 inches. The NFL lineman in 1950 was 6-2, so they too have gotten three inches taller while the batters grew an inch. Pitchers have gotten two inches taller. So yeah other sports have had bigger increases in height than baseball, but while they seem to have stopped getting bigger.
Generall pitchers have been two inches taller than hitters. For whatever reason that difference shrunk to one inch during the 1990s. According to the graph batter heights leveled off around 1989, but pitcher height started going up again around 2001.
http://www.azsnakepit.com/2010/7/5/1550963/baseball-players-does-size-matter
Anyway rereading the book the author seems to cherry pick his stats. His contention that NBA players are bigger is based on the heights of starting fives of NBA championship teams, and WS winners.
Pitchers are red batters are blue.
[SIZE=11pt]What has really changed is the weight of players, and lest we think roids were the reason the climb in weight has not slowed[/SIZE]
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Anyway I stated a thesis from a book, and the stat that most convinced there is an error is the number of huge DHs. Obviously these guys get their job purely to hit. Probably a limit on guys over 6-5 is the inability of giants to play well enough in the field. Likewise the higher pitcher height has to do with the fact every pitcher is a specialist, you don't have middle infielders in there bringing the height down.
I would propose the slower increase in hitter size is due to the great popularity baseball had in the early parts of the 20th century having a 50 year head start on getting elite athletes. And while the NBA seems to have reached a plateau where the size of players had a diminishing return, baseball reached that period earlier.