Via BBTF, the post 2015 All-Star major league ball does seem to be different. Mitchel Lichtman did something no reporter ever thought to do when writing on the subject of juiced balls:

Late last year, Lichtman commissioned independent ball-testing in an effort to confirm or refute the altered-ball hypothesis. First, he purchased 36 game-used MLB balls from eBay, each of which was authenticated for a particular game with an official MLB collector’s holographic sticker. Seventeen of the balls were used in games played prior to the 2015 All-Star break, ranging from May 2014 to July 2015. Nine were used in games in either August or September 2015, and the remaining 10 were used in May, June, or July 2016. The balls seemed to be in good condition, and the three groups were indistinguishable from each other by outward appearance and feel.

Excellent. There are two sets of balls from different time frames.

Lichtman sent the balls to one of the few facilities capable of rigorous testing, the Sports Science Lab at Washington State University. There, the balls’ CORs were tested by firing them at 120 mph into a steel cylinder, six times each, which is considered the closest approximation of in-game collisions that wouldn’t destroy the ball. The lab also measured the circumference and weight of the balls, the height of their seams, and their dynamic stiffness (a more sciencey way to say “hardness”). Before testing, all of the balls were stored for two weeks in a humidor with constant temperature and humidity to ensure consistent conditions, and randomly coded so that no one at the lab knew which balls came from each lot. (Lichtman kept the key that matched codes to baseballs.)

So it was a blind test. Also very good. It might have been nice to have a set of balls from ten or twenty years ago as a comparison also, but this looks like a very good setup. Lichtman also shares his data with the world.

The testing revealed significant differences in balls used after the 2015 All-Star break in each of the components that could affect the flight of the ball, in the directions we would have expected based on the massive hike in home run rate. While none of these attributes in isolation could explain the increase in home runs that we saw in the summer of 2015, in combination, they can.

What no one ever seems to do is call the manufacturer and ask point blank if they changed anything. I did call Rawlings in the mid 90s when people where talking about a juiced ball, and Rawlings told me they were building their most consistent ball ever. At the time, businesses in the US were adopting the Japanese business practice known as six sigma, which greatly reduces waste by stopping production when when the component produced is out of a particular tolerance. I’m fairly certain Rawlings applied this to baseballs, but instead of setting their tolerances for the middle range of baseball parameters (which are quite large in terms of diameter and weight), they set them at the high end. Setting things at the high end makes sense when the process is going to degrade over time; they can let the process run and still get legal baseballs. But constantly adjusting to the high end of the ball (tighter, smaller), they helped cause a home run explosion.

The article clearly points out that there does not need to be a concerted effort to make baseball go farther:

Even if MLB’s peak-power era began with a change in the baseball, that wouldn’t imply a plot at the highest levels of the league. Yes, a Ken Rosenthal report from January 2015 revealed that MLB had brought up the idea of juicing the ball, and yes, it does seem somewhat suspicious that the ball began flying just when fans and officials were fretting about run-scoring falling to its lowest level in almost 40 years. But modest alterations to multiple components of the ball could have gone undetected more easily than a massive alteration to one aspect. The change could have been an unintended consequence, just as it was when the Reach Company tried to cut costs on wool and ended up with a bouncier baseball. Even MLB’s testing and allowable range suggest that the ball varies slightly from batch to batch and year to year, and those slight differences might stack up in certain seasons.

So the ball is probably a little livelier than in early 2015. That’s okay, chicks dig the long ball. I do worry a bit that it’s helping move baseball closer to a three-true outcome game, and that would be boring.