BrianGriffin said:
Another result of integration was the trend toward improved defense that has never turned back. Simply put, if you take 100 balls struck in play in the exact same way in 1970 compared to 1940, I bet 5 or more of the balls hit in 1940 would be hits and a few of the hits would find their way to the wall for doubles or triples.
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Add that to the fact that players are bigger, stronger faster and it's clear to me that balls hit in play are less likely to land for hits and less likely to find their way to walls than they used to be.
BABIP measures for the first part of your statement. Believe it or not, balls were MORE likely to fall in for hits in 1940 than 1970, despite all the legitimate defensive and scouting advances you mentioned.
That said, I definitely think balls are less likely to find their way to the walls -- but that's more a product of modern field dimensions. Instead, they're more likely to find their way over the wall.
Just pulling some years out of a hat here, but here's some historical league BABIP figures, according to FanGraphs:
1918-1920: .289
1928-1930: .304
1938-1940: .289
1948-1950: .279
1958-1960: .278
1969-1971*: .276
1978-1980: .286
1988-1990: .285
1998-2000: .299
2008-2010: .300
*chose '69-'71 over '68-'70 so as to include all 24 teams
So balls are actually more likely to fall in for hits today than they were in 1970, too. Which makes sense when you think about how drastic of a pitcher's era that was. But that's the lowest average BABIP by far. Generally you're looking at somewhere around .290.
I realize a lot of people have violent reactions when they first encounter
Voros McCracken's theory on balls in play, and it's definitely a hard truth to accept. But the numbers don't lie.
BrianGriffin said:
Getting back to trends, would you say offense has declined in the last five-six years and if so, why? I agree with all your theories on what may have contributed to the home run splurge, but I'll add these comments:
-- Live ball theories have been around for decades. I think Ted Williams talks about it in Science of Hitting. And I think there's something to it, but those things don't cause long-term trends. A batch of tightly-wound balls may help cause an increase in production for the short-term, but unless the standard for making balls changes -- and it hasn't, significantly -- the variation from "batch" to "batch" will be a short-term thing.
This particular live-ball theory has some juice behind it, though. I'll repost Eric Walker's compelling evidence (originally mentioned here by BB Bobcat):
http://highboskage.com/juiced-ball.shtml#EXPANSION
Something happened in 1993-94, and it wasn't just steroids ... or a new team in Denver.