David Cone and Orel Hershiser

In Mauer's 2009, his GB/FB ratio and line drive percentage were pretty much the same as the rest of his career. But he managed a .373 BABIP (31 points above his career average) and 20.4% of his fly balls were home runs (almost double his next best full season, and slightly more than double his career average).

I don't want to say "lucky," but I think "unsustainable" is a good way to describe those stats.

 

Even with some of the guys who we know were juicing, and were already power hitters, you see these kinds of spikes.
Barry Bonds never hit more than 49 except for his 73-homer season.
Ken Caminiti had 40 in 1996, not more than 29 any other season (and all of his 20-plus seasons were during a four-year stretch from 1995-99 when he admitted he was using PEDs).
Gary Sheffield was consistently good for 30-35 homers most of his career, but jumped up over 40 twice.

Like RickStain said, it's not sustainable over a course of years, but for a few months or even a few weeks during a 162-game season where you get hot and pop a few more homers, it might just be something of a statistical anomaly.
I'm a lot less suspicious of the random one-year jumps that regress back to the mean, than I am of the guys like Bret Boone who go from 20-homer power to 30-35 homer power overnight and then maintain it for several years.

 

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.

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.

 

I definitely think this is the case, which is why I posted Tommy Davis' stat line above. It's baseball, and weird shit happens, like a Mendoza-line Dan Uggla having the best hitting streak in the majors this year. With 1,000+ players in the majors each year, you're going to get fluke results.

Again, Jonah Keri had a good column on this when talking about people trying to link Bautista's success to steroids or sign stealing, and Malcolm Gladwell has done extensive writing on it in general. As humans, we look for connections and causation in everything, even when there might not be any. Every once in a great while, a baseball player is just going to have a great year or improve unexplained for the rest of his career.

 

I don't get your point. With improved defenses, you'd expect the batting averages in 1970 to be lower than in 1940 and they were, in both leagues (.271 in 1940, compared to .250 in 1970 in the AL and .264 in 1940 compared to .258 in 1970 for the NL). Of course, it's worth noting in 1970, batting averages were coming off their long-time (all-time?) lows after MLB lowered the mound for the 1969 season.

You'd also expect to see a surge in offensive production numbers in 1973, the year the DH was added. While the NL numbers stayed generally in the .250s until the steroid era (they have since dipped back), the AL numbers went up to the .260s, reflecting the extra hitter in the lineup. Of course, those numbers jumped in the steroid era and have since dipped.

 

Hmm, I think I misread your statement. Your 1940 to 1970 comparison was accurate, and the numbers showed it.

But this claim:

... is only half-correct. Balls are MORE likely to fall in for hits these days. And that's what I was trying to show through historical BABIP.

However, they are less likely to find their way to walls. That's because they're much more likely to find their way over the wall these days.

Either way, I don't see how the '90s-'00s power trend is ALL about steroids. There are a lot of factors in play here.

 

I think the author dismisses things not worth dismissing.

We know there can be tipping points in starting trends. If a couple of high-profile mavens catch the eye of some influential connectors (in Gladwell-speak), the use of performance-enhancers can go from marginal to widespread literally overnight and can cause a sudden surge, that can sustain if it becomes the new norm, which it evidently did.

Here's what's interesting: One trend can start another. I noted with interest that babip has increased even as overall numbers declined. Could this be the result of a de-emphasis on defense in player development in the offensive 90s?

I remember covering college baseball in the "nuclear bat" era of the late 90s, and seeing coaches take slow, corner infielders and moving them up the middle to add more double-digit home run power to the lineup. The fielder-first player was irrelevant with so many games decided by un-catchable balls beyond the wall.

Was there a negative trend on defensive performance this decade as a residual of the last decade?