Could the baseball be responsible for surge in HRs in 2015?

Even the Citi Field apple was hit hard by the increase in homers this past season.

Anthony Gruppuso/Anthony Gruppuso-USA TODAY Sport

I’ve got a mystery for you, which I’ve saved until Friday for the sole purpose of spoiling your weekend, since you won’t be able to think about anything else.

Something strange happened in 2015.

Actually, a lot of strange things happened. But I’m just talking about baseball, and I’m not talking about the Kansas City Royals. No, I’m talking about the crazy surge in power hitting that a lot of people actually missed.

For the full monty on this phenomenon, I highly recommend tracking down a copy of "The Hardball Times Baseball Annual 2016," which includes a fine treatise by our old friend Jeff Sullivan.

As Jeff points out —€“ and as incoming Commissioner Rob Manfred must surely have been aware — scoring has dropped steadily since PITCHf/x systems were installed in every stadium, which presumably led to umpires calling the technically "correct" strike zone with greater frequency. As it turned out, the correct strike zone was a larger strike zone, and friendlier to the pitchers. From 2000 through 2010, scoring held reasonably steady, averaging between 4½ and five runs per nine innings in every season. But from 2011 through ’14, the average was between four and 4½ runs per nine innings in every season.

All of this has been well-documented in many places.

What happened in 2015 has not been.


Before the All-Star break, there were 4.10 runs per nine innings, a fair match for the entire 2014 season. But in August, scoring jumped to nearly 4.5 per nine innings, and stayed there in September.

What happened?

The strike zone didn’t change. Strikeout rates didn’t change, nor did walk rates. Batting average on balls in play held fairly steady.

Which leaves essentially one thing: HOME RUNS.

And whaddayaknow, home runs were way, way up in 2015. They were up not because all those big boys were making more contact (again, they weren’t) but rather because when they did make contact, a significantly higher percentage of batted balls were flying over the outfield walls. In the second half of 2015, 4.1 percent of batted balls became home runs. That 4.1 percent is one of the five highest half-season percentages since the 2000 season … and (here’s the kicker!) three of the other four were in 2000 and 2001 (with the fourth in 2004).

What was happening in 2000 and 2001?

Some of you might recall what later came to be known as THE STEROID ERA.

But hold on for a moment. We’ll get back to the sports drugs in a minute or two. Jeff wonders what could account for this huge increase in HR/Contract Percentage.

Warmer temperatures? It was warmer in the second half last season than usual. But as Jeff writes, "physics-of-baseball authority Alan Nathan figures this doesn’t get you too far." Not far at all, actually.

All those great rookies? Yeah, somewhat. Jeff has rookie hitters and pitchers being responsible for an extra 250-some home runs. But home runs were up by 723 from 2014 to 2015. Also — and maybe I’m missing an important piece of Jeff’s analysis here —€“ if the general conditions favored power hitting, wouldn’t rookies naturally hit more home runs than otherwise? Which isn’t to discount Kyle Schwarber and Kris Bryant and all the rest of them.

So if it wasn’t the weather or (largely) the rookies, what was it?


I’ve never met anybody who works for a baseball team and doesn’t attribute the power surge in the Steroid Era to … well, to steroids. I’ve never met anybody who doesn’t believe power surged because of sports drugs, and then fell when baseball started cracking down on the sports drugs.

Conventional Wisdom is usually correct, or mostly correct.

But it’s not always correct.

In 1987, there was a HUGE power surge and it’s never been explained.

Of course, the power surge that began in the late 1990s has been explained. Explained in any number of accusatory books. The explanation has kept a bunch of guys out of the Hall of Fame.

But there’s another explanation. Jay Jaffe, for one, has cited evidence that the baseball was livelier in that same era. J.C. Bradbury has written much the same, and suggests that we should call it the Home Run Era instead.

You might think it’s all just a crazy conspiracy theory, and I suppose you’re probably right. But every once in a while, the crazy people are actually right.

So there’s your mystery. And if you happen to be a working baseball writer, and particularly a working baseball reporter, here’s my challenge to you …

Find out. Or at least try to find out. As far as I know, not a single reporter has ever tracked down people who work at MLB’s highest level, or used to, and asked them about the baseballs in 1987 and 1998 and 2001. As far as I know, not a single reporter has tracked down a dissatisfied ex-Rawlings employee, or a former mid-level manager at the factory in Costa Rica, with questions about changes to the baseball over the years. As far as I know, nobody’s recently tested the baseballs with the latest technology, to see if 2015 baseballs were any different from 2013 baseballs.

There are a lot of reporters. Thanks to Twitter, we only need about three of them to focus on Brandon Phillips’ financial needs. I would be thrilled if a few of the others would get to work on the biggest baseball mystery in my lifetime.