A cool article, laid out to be readily understandable for everyone.
Missing from the discussion, though, is a description of the change in the moment of inertia. If the ball's mass distribution has shifted radially, the moment of inertia can change significantly.
Spin matters very much to the aerodynamics of baseballs. A change in the moment of inertia could have a substantial impact (positive or negative) on the flight characteristics as the ball reaches the batter, the mechanics of the ball/bat interaction (particularly as relates to the spin of the ball leaving the bat), and the outbound trajectory. A lower-moment ball will spin faster initially, but slow its rotation rate more quickly, making any prediction of the overall effect of a change in moment of inertia difficult indeed.
It's funny, because based off the header image on that page [0], that's what I expected the discussion to be about. The center of gravity in those four samples is hugely off.
If you scroll down further in the article, you'll see that those are cropped images of the cores. The cropping is off-center, not the cores. Otherwise, they would wobble terribly when thrown or hit.
This single paragraph is all the specifications for a legal ball in baseball[0]:
> 3.01 (1.09) The Ball
> The ball shall be a sphere formed by yarn wound around a small core of cork, rubber or similar material, covered with two strips of white horsehide or cowhide, tightly stitched together. It shall weigh not less than five nor more than 5 ¼ ounces avoirdupois and measure not less than nine nor more than 9 ¼ inches in circumference.
So it leaves a lot of wiggle room, intentional or not, for modifying the baseball to produce different results. As the article points out, 2014 was a great year for pitchers with the fewest home runs since 1995. And that year, 1995, is significant as that was the year of the strike shortened season.
I'm still on the fence as to whether this is a good or bad thing (juiced balls) as in the 20s there were rule changes regarding how balls were treated that led to the live ball era[1] and the greatest baseball legend, Babe Ruth.
Baseball has a way of balancing out over time, so we may see a wild homerun heyday before getting a period of pitching dominance. Both super fun to watch.
The article says the newer balls differed in mass by 0.5 grams and that this difference was statistically significant
For reference the "not less than five nor more than 5 ¼ ounces avoirdupois" in that rule means
141.747615625 to 148.83499640625 grams. (Yes exactly, the "pound avoirdupois" no longer has any definition except that it's so-and-so many SI kilograms).
So 0.5 grams is a pretty big change, but it's way inside the variation allowed. Given the change in composition it seems to me that such a change is to be expected and actually suggests the ball makers did NOT go out of their way to hide what's happened here.
Naturally since MLB baseballs are basically hand-made. I've seen any number of segments showing how they're manufactured. Very low tech - winding by machine but the covers are sewed on by hand.
Statistics are always a two-edged sword. Using home run statistics to "prove" a ball had changed is folly unless you have the data on balls over many years including the variance which as you pointed out can be significant.
If MLB did this deliberately without the consent of the teams, some owners might be upset.
As the article points out, players are already adapting their hitting approach to produce more home runs, and presumably that’s at least partially due to the added likelihood of success for that strategy with the juiced balls.
So of course there’s also a team-building aspect of this shift for GM’s to consider. A decade ago, all the smart money was on high “OBP” (on-base percentage) players over boom-or-bust power hitters. If MLB did juice the ball, it shifted the ground out from under tens of millions of dollars of team analytics, and billions in payroll decisions made based on them.
>A decade ago, all the smart money was on high “OBP” (on-base percentage) players over boom-or-bust power hitters.
That is not an entirely accurate characterization, in fact most of the time the moneyball teams valued those boom and bust players more than traditional teams. The actual equation they were using was something close to 3*OBP+Slugging so slugging is good, and they tend to get walks a lot along with their strikeouts so OBP is usually good too.
Yep, "three-true-outcomes" (HR, strikeout, walk) players were seen as undervalued. Much of today's developments can be seen as flowing out of that re-evaluation of the "badness" of strikeouts.
OBP driven by consistent-but-weak contact was the sort of thing that sabermetrics types in 2008ish were shifting away from. Adam Dunn types (high OBP power hitter, low average) were seen as undervalued compared to Juan Pierre types (low power, higher average).
Fun thing about Pierre vs Dunn - Fangraphs has them practically tied in career WAR in the same number of seasons. But traditional evaluations praised the scrappy Pierre types a lot more than the strikeout-happy Dunn types.
While you're kind of right, I downvoted because I don't think that's the most reasonable or fair interpretation of what they're saying.
I think their point is largely true in two or three ways. The first is that prior to the moneyball era, teams treasured power hitters in a way that was much more OBP agnostic.
The second way is that they underappreciated players who don't hit for power but put up strong OBPs, like Scott Hatteberg.
The third is that however much moneyball teams prized home runs, they certain prize them even more now than before.
I think it's perfectly fair to say these distinctions support the notion that moneyball teams didn't value power hitting the same way as the generations that preceded or followed them.
There's an assumption that Major League Baseball cares about fair competition and integrity, but those things are much less important than you might think.
In the 1990s, a very large number of players used performance-enhancing drugs (PEDs). Those who were honest and declined to use them were penalized by being less competitive (a problem any time you allow corruption - the market favors the corrupt and weeds out the honest), undoubtedly some losing their jobs and dreams.
MLB did nothing, other than to change the rules and ban the use of the drugs. The cheaters suffered no penalties and their records stand; the victims, including honest players as well as fans, no compensation or even official acknowledgement (that I know of). One of the most prominent cheaters has a job as a coach on major league teams, including as a hitting instructor for many years. Another had his jersey retired by his team and was inducted into their team Hall of Fame, and now has a job with them. (The cheaters are having a hard time getting into the national Hall of Fame, but that's due to sportswriters and others voting against them, and they are coming closer each year.)
Does MLB care if the balls are juiced, or if current players have discovered new ways to cheat?
This article really does a good job of making this topic accessible to those of us that live outside of the 'land of the free'. The graphics and UX are really neat.
The research does prove that the ball has changed.
However, the composition of the ball has changed many times over the years with new technology and new rules. It should be possible to look back at when the core changed from rubber to cork (for example) and to see the effects this has had. This bigger narrative could be useful in understanding what has gone on lately.
Exit velocity and launch angle of the ball have only been recorded since 2014. 2015 league-wide. That's why this latest change is causing all this analysis.
Is anyone else surprised by the sample size? I'm not sure that eight baseballs provides enough data for any relevant conclusions, especially when the differences are so small to begin with.
Assuming there has always been 50% light balls and 50% heavy balls, the probability of picking 4/4 heavy balls from the earlier period and 4/4 light balls from the later period by chance is 0.4%.
Although this statistic might be less relevant if the balls were not statistically randomly selected.
If all the balls have shown variations within the same tolerances, that would be true, but balls grouped in a meaningful way, and these groups have shown negligible differences among themselves.
Because of this tight variation within the groups, 8 balls are enough IMHO.
Similar discussion on cricket ball and how science shows no impact of weather on balls flying through air significantly enough but still remains a common misconception through out the sport's fraternity.
It's certainly been discussed in the forums I've read, and it could certainly account for some of it, but the mid-season spike in home runs starting in 2015 seems to point to at least one additional factor that would be somewhat consistent across all ballparks (including climate controlled). The balls seem to be one of the only factors that would account for that.
Air density does have an effect, but the density change from temps that we've seen in the last few years (say a 75 degree game vs an 80 degree game) is only going to get you a couple feet of ball travel. While it make a difference on balls that just barely clear the fence, it definitely doesn't account for the entire boom in home runs.
For comparison, a ball hit 400 ft at Yankee Stadium (400 ft elevation) would go 440 ft at Coors Field (5280 ft elevation). That's a 10% increase in ball distance for a 17% decrease in density. Increasing the temp by 5 degrees F drops the density by 0.8%, which is probably only good for 1-3 feet.
Readit News
Missing from the discussion, though, is a description of the change in the moment of inertia. If the ball's mass distribution has shifted radially, the moment of inertia can change significantly.
Spin matters very much to the aerodynamics of baseballs. A change in the moment of inertia could have a substantial impact (positive or negative) on the flight characteristics as the ball reaches the batter, the mechanics of the ball/bat interaction (particularly as relates to the spin of the ball leaving the bat), and the outbound trajectory. A lower-moment ball will spin faster initially, but slow its rotation rate more quickly, making any prediction of the overall effect of a change in moment of inertia difficult indeed.
[0]: https://espnfivethirtyeight.files.wordpress.com/2018/03/juic...
sorry
> 3.01 (1.09) The Ball
> The ball shall be a sphere formed by yarn wound around a small core of cork, rubber or similar material, covered with two strips of white horsehide or cowhide, tightly stitched together. It shall weigh not less than five nor more than 5 ¼ ounces avoirdupois and measure not less than nine nor more than 9 ¼ inches in circumference.
So it leaves a lot of wiggle room, intentional or not, for modifying the baseball to produce different results. As the article points out, 2014 was a great year for pitchers with the fewest home runs since 1995. And that year, 1995, is significant as that was the year of the strike shortened season.
I'm still on the fence as to whether this is a good or bad thing (juiced balls) as in the 20s there were rule changes regarding how balls were treated that led to the live ball era[1] and the greatest baseball legend, Babe Ruth.
Baseball has a way of balancing out over time, so we may see a wild homerun heyday before getting a period of pitching dominance. Both super fun to watch.
0: http://mlb.mlb.com/mlb/official_info/official_rules/official...
1: https://en.wikipedia.org/wiki/Live-ball_era
For reference the "not less than five nor more than 5 ¼ ounces avoirdupois" in that rule means 141.747615625 to 148.83499640625 grams. (Yes exactly, the "pound avoirdupois" no longer has any definition except that it's so-and-so many SI kilograms).
So 0.5 grams is a pretty big change, but it's way inside the variation allowed. Given the change in composition it seems to me that such a change is to be expected and actually suggests the ball makers did NOT go out of their way to hide what's happened here.
Statistics are always a two-edged sword. Using home run statistics to "prove" a ball had changed is folly unless you have the data on balls over many years including the variance which as you pointed out can be significant.
As the article points out, players are already adapting their hitting approach to produce more home runs, and presumably that’s at least partially due to the added likelihood of success for that strategy with the juiced balls.
So of course there’s also a team-building aspect of this shift for GM’s to consider. A decade ago, all the smart money was on high “OBP” (on-base percentage) players over boom-or-bust power hitters. If MLB did juice the ball, it shifted the ground out from under tens of millions of dollars of team analytics, and billions in payroll decisions made based on them.
That is not an entirely accurate characterization, in fact most of the time the moneyball teams valued those boom and bust players more than traditional teams. The actual equation they were using was something close to 3*OBP+Slugging so slugging is good, and they tend to get walks a lot along with their strikeouts so OBP is usually good too.
OBP driven by consistent-but-weak contact was the sort of thing that sabermetrics types in 2008ish were shifting away from. Adam Dunn types (high OBP power hitter, low average) were seen as undervalued compared to Juan Pierre types (low power, higher average).
E.g. http://www.firejoemorgan.com/2008/03/this-column-is-eternal....
Fun thing about Pierre vs Dunn - Fangraphs has them practically tied in career WAR in the same number of seasons. But traditional evaluations praised the scrappy Pierre types a lot more than the strikeout-happy Dunn types.
I think their point is largely true in two or three ways. The first is that prior to the moneyball era, teams treasured power hitters in a way that was much more OBP agnostic.
The second way is that they underappreciated players who don't hit for power but put up strong OBPs, like Scott Hatteberg.
The third is that however much moneyball teams prized home runs, they certain prize them even more now than before.
I think it's perfectly fair to say these distinctions support the notion that moneyball teams didn't value power hitting the same way as the generations that preceded or followed them.
https://twitter.com/JustinVerlander/status/96939000476931686...
Seems the balls are flying farther?
In the 1990s, a very large number of players used performance-enhancing drugs (PEDs). Those who were honest and declined to use them were penalized by being less competitive (a problem any time you allow corruption - the market favors the corrupt and weeds out the honest), undoubtedly some losing their jobs and dreams.
MLB did nothing, other than to change the rules and ban the use of the drugs. The cheaters suffered no penalties and their records stand; the victims, including honest players as well as fans, no compensation or even official acknowledgement (that I know of). One of the most prominent cheaters has a job as a coach on major league teams, including as a hitting instructor for many years. Another had his jersey retired by his team and was inducted into their team Hall of Fame, and now has a job with them. (The cheaters are having a hard time getting into the national Hall of Fame, but that's due to sportswriters and others voting against them, and they are coming closer each year.)
Does MLB care if the balls are juiced, or if current players have discovered new ways to cheat?
The research does prove that the ball has changed.
However, the composition of the ball has changed many times over the years with new technology and new rules. It should be possible to look back at when the core changed from rubber to cork (for example) and to see the effects this has had. This bigger narrative could be useful in understanding what has gone on lately.
https://en.wikipedia.org/wiki/Baseball_(ball)
Although this statistic might be less relevant if the balls were not statistically randomly selected.
Because of this tight variation within the groups, 8 balls are enough IMHO.
Warm weather -> less dense air -> balls fly farther. Recent years have been record warm. Does that have any measurable or meaningful effect?
http://theconversation.com/why-we-think-the-weather-affects-...
For comparison, a ball hit 400 ft at Yankee Stadium (400 ft elevation) would go 440 ft at Coors Field (5280 ft elevation). That's a 10% increase in ball distance for a 17% decrease in density. Increasing the temp by 5 degrees F drops the density by 0.8%, which is probably only good for 1-3 feet.
https://chem.libretexts.org/Exemplars_and_Case_Studies/Exemp...
https://wahiduddin.net/calc/calc_da.htm