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.
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.
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.
Baseball is such a data-driven sport, and numbers don't tend to lie. There's always always some new form of juice, some changes to the mound, something going on with the bats and balls...
Do the materials in a baseball show up differently over time, say over a 20-30 year span? I'd really want to see this done on more sets of baseballs. In addition to testing players, if the goal was consistency it would be prudent to scan the balls, do a core sample of the pitcher's mound every game, make sure bat composition and temperatures are consistent... The new pitch clock isn't going to empower pitchers either though, look for batter power to rise again next year.
Definitely, here is a key sentence: "The decrease in drag is probably a result of a smaller, slicker baseball with lower seams."
The article ignores the fact that it is air resistance on the seams that creates the "break" in a curve ball. Less drag, less effective curves, ergo, advantage to the batter. So more HRs might come from less effective pitching.
The MLB might be well-advised to accept this analysis (together with FiveThirtyEight's previous analysis suggesting that the rest of the uptick might be explained by an increase in batters swinging upwards), as one alternative putative explanation for this uptick would be that there has been a development of new and undetectable methods of doping.
Can exit (exit from bat) velocity, trajectory and spin be measured and used with the climate conditions at time of hit to compute an expected batted ball distance which could then be compared to actual batted ball distance, with changes over time identifying possible ball changes?
Something I didn't see covered in the article (maybe I missed it) was a discussion of errors. If the ball is moving faster and potentially with more bounce, wouldn't we also expect to see an uptick in fielding errors?
Possibly, but this would somewhat be countered by the fact that you can’t get a fielding error on a home run.
Edit to add more context:
Home runs are much more common than errors - in 2017, there were a total of 2,820 errors, less than half the number of home runs. One of the more common types of fielding errors is dropping a fly ball, so it wouldn’t take a huge percentage of would-be dropped fly balls converted to home runs to counter any uptick in fielding errors due to the ball being bouncier.
This smacks of some kind of inadvertent formulation change (like a company started buying a component from a new supplier that met whatever specs they were measuring, but resulted in a ball with significantly different characteristics). Now that's it's been a couple of years, the MLB is not going to change it back.
Heard a segment on this on Pardon the Interruption on ESPN yesterday. I agree with their argument that it's not a bad thing because we are in a time of sports where games need to be more exciting. We want more home runs, and more scorings, and if lighter baseballs means that we get them, then it's just a normal progression.
in a time of sports where games need to be more exciting
There's a problem with this, though. Home runs are only exciting when they're relatively uncommon. If the home run trend continues, we will effectively see the disappearance of everything else that makes up the game of baseball. Players will either hit a home run, a flyout, or a strikeout. Risky plays (small ball) such as hit-and-runs, sacrifice bunts, and stolen bases will see a continued decline. This will sap all of the strategy and nuance out of the game, turning it into pure spectacle.
Not what I want. Not what a lot of baseball fans want.
> we are in a time of sports where games need to be more exciting
Not just games, but everything from the US (I live in Europe) seems to need to create spectacles where there are none with as much flashbang as possible. Just look at the difference in BBC documentaries vs ones coming from the US.
This trend kicked into high gear around 2000 and I had to stop watching channels like Discovery as they no longer aired documentaries but entertainment shows.
In the end, I stopped watching TV altogether as a result of this and we haven't had a TV subscription of any kind since around 2005. My wife uses Netflix once or twice a month though when my sister visits.
If we accept lighter baseballs as a way to get more home runs, what's wrong with corked bats or any other mechanical mechanisms that could be used to juice home runs? Sammy Sosa was suspended 8 games for using a corked bat, which was claimed was supposed to only be for practice and was used accidentally.
I imagine someone at Ralings ”refining” the process and then placing bets for the season on number of homers or some other metric that would payoff.
If it is in fact a variation, one should be able to create a subscription service that sends out regular testing results on the balls, along with bets that capitalize on the information asymmetry.
[+] [-] ISL|8 years ago|reply
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.
[+] [-] ComputerGuru|8 years ago|reply
[0]: https://espnfivethirtyeight.files.wordpress.com/2018/03/juic...
[+] [-] snovv_crash|8 years ago|reply
[+] [-] tomcam|8 years ago|reply
sorry
[+] [-] adregan|8 years ago|reply
> 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
[+] [-] tialaramex|8 years ago|reply
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.
[+] [-] SpikeDad|8 years ago|reply
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.
[+] [-] twoodfin|8 years ago|reply
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.
[+] [-] gameswithgo|8 years ago|reply
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.
[+] [-] kurtisc|8 years ago|reply
[+] [-] KC8ZKF|8 years ago|reply
https://twitter.com/JustinVerlander/status/96939000476931686...
Seems the balls are flying farther?
[+] [-] forapurpose|8 years ago|reply
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?
[+] [-] Theodores|8 years ago|reply
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)
[+] [-] KC8ZKF|8 years ago|reply
[+] [-] whatisunseen|8 years ago|reply
[+] [-] mortehu|8 years ago|reply
Although this statistic might be less relevant if the balls were not statistically randomly selected.
[+] [-] bayindirh|8 years ago|reply
Because of this tight variation within the groups, 8 balls are enough IMHO.
[+] [-] Tarrosion|8 years ago|reply
Warm weather -> less dense air -> balls fly farther. Recent years have been record warm. Does that have any measurable or meaningful effect?
[+] [-] ofcrpls|8 years ago|reply
http://theconversation.com/why-we-think-the-weather-affects-...
[+] [-] stinkytaco|8 years ago|reply
[+] [-] olympus|8 years ago|reply
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
[+] [-] dbg31415|8 years ago|reply
* Baseball just saw its biggest home run surge since the steroids era. Here’s why. - The Washington Post || https://www.washingtonpost.com/news/fancy-stats/wp/2016/03/0...
The real graph to pay attention to: https://img.washingtonpost.com/wp-apps/imrs.php?src=https://...
Do the materials in a baseball show up differently over time, say over a 20-30 year span? I'd really want to see this done on more sets of baseballs. In addition to testing players, if the goal was consistency it would be prudent to scan the balls, do a core sample of the pitcher's mound every game, make sure bat composition and temperatures are consistent... The new pitch clock isn't going to empower pitchers either though, look for batter power to rise again next year.
[+] [-] Someone|8 years ago|reply
It suggests the lower air resistance makes pitchers throw faster, too.
I would think lower ridges also made pitchers throw more predictable balls. That may have made going for a big hit a more profitable strategy.
[+] [-] fernly|8 years ago|reply
The article ignores the fact that it is air resistance on the seams that creates the "break" in a curve ball. Less drag, less effective curves, ergo, advantage to the batter. So more HRs might come from less effective pitching.
[+] [-] mannykannot|8 years ago|reply
[+] [-] maxerickson|8 years ago|reply
Combine that with moderate improvements in training and there you go, 35 year olds that can train like they are 20.
[+] [-] gz5|8 years ago|reply
[+] [-] stretchwithme|8 years ago|reply
[+] [-] poulsbohemian|8 years ago|reply
[+] [-] djrogers|8 years ago|reply
Edit to add more context: Home runs are much more common than errors - in 2017, there were a total of 2,820 errors, less than half the number of home runs. One of the more common types of fielding errors is dropping a fly ball, so it wouldn’t take a huge percentage of would-be dropped fly balls converted to home runs to counter any uptick in fielding errors due to the ball being bouncier.
[+] [-] joncrane|8 years ago|reply
[+] [-] rvshchwl|8 years ago|reply
[+] [-] chongli|8 years ago|reply
There's a problem with this, though. Home runs are only exciting when they're relatively uncommon. If the home run trend continues, we will effectively see the disappearance of everything else that makes up the game of baseball. Players will either hit a home run, a flyout, or a strikeout. Risky plays (small ball) such as hit-and-runs, sacrifice bunts, and stolen bases will see a continued decline. This will sap all of the strategy and nuance out of the game, turning it into pure spectacle.
Not what I want. Not what a lot of baseball fans want.
[+] [-] tyfon|8 years ago|reply
Not just games, but everything from the US (I live in Europe) seems to need to create spectacles where there are none with as much flashbang as possible. Just look at the difference in BBC documentaries vs ones coming from the US.
This trend kicked into high gear around 2000 and I had to stop watching channels like Discovery as they no longer aired documentaries but entertainment shows.
In the end, I stopped watching TV altogether as a result of this and we haven't had a TV subscription of any kind since around 2005. My wife uses Netflix once or twice a month though when my sister visits.
[+] [-] PakG1|8 years ago|reply
https://en.wikipedia.org/wiki/Corked_bat#History_of_use_in_M...
I suppose like any other sport, baseball is picky and arbitrary about what's OK and what's not OK when it comes to changing equipment and standards.
[+] [-] ada1981|8 years ago|reply
If it is in fact a variation, one should be able to create a subscription service that sends out regular testing results on the balls, along with bets that capitalize on the information asymmetry.
[+] [-] LoonyBalloony|8 years ago|reply
[+] [-] anonu|8 years ago|reply
Nonetheless, good research...
[+] [-] thom|8 years ago|reply