THE BOOK--Playing The Percentages In Baseball

Yes, I thought this was a very interesting piece.

On the HRs, it seems possible to me that hitters did start driving the outside pitch much more in the mid/late-90s, but that pitchers then found ways to adjust, driving the percentage of opp-field HRs back to its historical rate.  Certainly the initial rise looks big enough to be something real.  Not sure how we would test this theory, though.  Perhaps look for evidence that pitchers starting pitching inside more after 2000, at least to power hitters?  The 30% increase in HBP between 1999 and 2006 is one piece of supporting evidence.

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On the gap btwn LH and RH hitters for opp-fld doubles, I don’t think the superiority of RF arms can possibly account for such a large difference.  I’d guess that for some reason it’s easier to hit an opp-field double when you have the platoon advantage, or there’s some other reason that LHs do this more often.

The jumps in % of opposite field homeruns trend with the overall level of homeruns hit.  The theory that seems most logical to me is that the ball was juiced.

Rally:  But why would a juiced ball change the distribution of HRs?  And why would the change in opp-field % be so much larger than the change in HR rates?

My guess would be that pulled HR are more likely to be HR with or without the extra juice, but the opposite field HRs need that extra juice to get out of the park.

Rally:  Under this theory, two things need to be true:

1) Other factors have propped up the HR-rate as the ball got “de-juiced,” such as strength-training, new parks, better bats, etc.  (Otherwise, we’d be back to 1992 HR rates); and

2) These other HR-increasing factors do not serve to increase the proportion of opp-field HRs, whereas a juiced ball does. 

I think #1 is likely true, but it’s hard to see why #2 would be.  If the theory is that hitters hit more warning-track FBs to the opposite field under “normal conditions,” then any of these factors should presumably raise the opp-field proportion.

It looks like, while opp field HR have jumped up and down, there is a general trend upwards. We’ve got a greater % of opp field HR now than in the 80’s, even after the HR peak of 96-00 has passed.

So the other reasons for HR increase also increase the opposite field percentage.  The general trendline represents longterm changes in the game, and the spikes could be where the ball was juiced.

Or at least that’s my guess.

Should have thought of this earlier:  a major reason that LHBs hit more opp-field doubles is that it’s much harder for them to hit opp-field triples, as John shows (much shorter throw from LF to 3B).  So some LHB-doubles are triples when a RHB hits an equivalent ball.  Conversely, when a LHB pulls a ball down the line, it’s much more likely to become a triple—reducing the proportion of his same-field doubles—while almost all pulled balls by RHBs will be limited to a double.  While there aren’t a lot of triples hit, since this analysis only includes airballs, and excludes balls fielded by CFs, this could explain most/all of the gap.

Still, I’d like to see this broken down by pitcher-handedness, to see if that explains some of the difference.

Guy, fantastic point.  Silly of us not to have noticed.

When I do this kind of stuff, I *always* lump 2B+3B together, since a 3B is a legged-out double.  (Ideally, we’d like to also include 1B+thrown out at 2B.)

And when it comes to 3B, I always do: 3B/(2B+3B), since that’s the opportunity factor.

Maybe John can rerun…

Tango: thanks for the kind words!

Guy: yes, great insight on the doubles/triples issue. Definitely sounds more plausible than my hypothesis.  I will have a look at the 2B+3B opp-field ratio and report back.

Rally: my own theory is similar to yours, that ordinary fly balls (not smoked line drives) are most helped by extra “juice” and the correlation between fly balls and the opp-field would produce the observed increase in the ratio. My “juice”, though, includes any effect like PEDs, smaller parks, thin-handled bats, weight-training, etc.

I think the post-2000 decline in opp-field HRs is probably BOTH a function of the overall reduction in HR rate (as Rally suggests) and some effective counter-strategy by pitchers.  Otherwise, the proportions don’t make sense:  the recent decline in HR rate has been much smaller than the 1993-2000 increase, yet the earlier increase in opp-fld HRs has been almost entirely eliminated.  Also, the increase in HBP rates is pretty dramatic—pitchers clearly are trying to push hitters back so they can’t whack the outside pitch quite as hard.

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The idea of separating the juiced ball from other HR-increasing factors is interesting and does a nice job of explaining the data.  The huge and sudden surge in 1993 and 1994 can’t be explained by evolutionary factors like weight training or lighter bats.  So I’m persuaded that the ball was juiced, deliberately or not.  But after the craziness of ‘98-99, MLB probably decided that—even though chicks love the long ball—they were in danger of having too much of a good thing (if only because of the length of games).  So the ball gets de-juiced.  However, the other factors that had continued to raise the HR-rate even after the 1993-94 surge were still at work, so a neutral ball had the effect of reducing offense, but not taking it back to the 1992 level.

Lefties will also get a few more doubles that would be singles by righties because they are a step closer out of the box.

Anyway, I think that a lot of the HR trending is due to two things:  One, where the pitcher pitches and two, where the batter stands.

Hitters stand closer to the plate for three reasons:  One, body armor, two, umpires don’t let pitchers intentioanlly hit batters anymore, and three, most importantly, because the strike zone is much lower and they don’t have to fear the high, inside strike.  As soon as the strike zone of the 60’s and 70’s (I don’t know about before then), where a letter high pitch was a strike, disappeared, which it did sometime in the late 70’s or early 80’s (I think), batters immediately moved closer to the plate.  If you are a batter, you would want to and you would have to.

As far as pitchers are concerned, the location of their pitches reflects exactly the same thing.  As soon as the strike zone was lowered (again, it was CONSIDERABLY lowered around the 80’s or so), pitchers stopped pitching inside, which they should.  If you can’t gete a high strike, there is no reason to pitch inside (I mean fewer inside pitches of course).  Low inside pitches or pitches that are a few inches too much toward the plate (middle-in) get crushed.  If you can throw a high pitch for a strike (like you could in the 60’s and 70’s), then even if you missed a little toward the plate it was no big deal.  Nowadays, if you try to throw inside too much, you will NOT get a called high strike, the batter will not swing at a high inside pitcher, you will hit the batter as he now stands closer to the plate, or you will give up a lot of home runs.  Pitchers can simply not throw inside nearly as much as they did when the strike zone was high.

One last thing which makes batters stand closer to the plate and pitchers pitch away more.  The greater strength of batters today and lighter bats.  Both of these things make bat speed quicker.  Quicker bat speed means better contact on inside pitches.

So basically batters stand much closer to the plate and pitchers pitch away more often. This equals more opp field HR’s, plain and simple.  It also means more opp field doubles, BUT the exta home runs take away some of the doubles, cancelling that affect out.  Remember that some doubles are home runs that don’t make it over the wall.  Also, when you hit the ball the other way, you hit more fly balls and fewer ground balls, as John pointed out.  Since some doubles are ground balls down the line, opp field hits also take away some of the those ground ball doubles.

So why has the trend reversed since around 2001?  Simple. The strike zone was changed in 01.  It became higher, although not nearly as high as it used to be.  Pitchers now pitch a little more inside and batters have to back away from the plate a little.  You will also probably see fewer opp field home runs based on fewer players using PED’s.