Home-Run Environment And Win-Homer Correlation

Home runs are good, I think we can all agree on that, and in the presumably post-steroid environment they have been in decline.  Does that make the home run more or less important?  It is hard to say.  In some ways it means that they are more scarce, and you might expect that home run hitting teams might be at a larger advantage than previously.  On the other hand, teams that don’t hit a lot of balls out of the park will not be as far behind their peers if said peers are not taking the ball yard quite so frequently.  So which is it?

FanGraphs, of course, can give the answer.  I took every team in the expansion era (1961 and on) and then tracked two things year over year.  The first was how far each team was from the average home runs for a team, just home runs for a team minus the average of all MLB teams.  From there I calculated the correlation of those differences with the wins that the team accumulated in that year.  Then I tracked that correlation versus the overall home run environment.  To get them in the same scale I tracked home run environment as a percent of the max average home runs per team, so 2000 became 100%, or peak home run environment, as it was the highest average per team and every other year the average was some percent below that with the average in 2000 as the denominator.

I did omit 1994 and 1981 due to how much the seasons were shortened by strikes.  It made the overall graph harder to read.  The results look like this:


 photo HRenvironment_zps35a42fa7.jpg


And the answer is…it doesn’t matter!  Home runs are always positively correlated with wins, meaning it is never advantageous for a team to be below average when it comes to hitting home runs.  That correlation over time has a best fit line with a near zero slope.  Home runs are equally valuable with respect to winning in lower home run environments and the more recent high ones.  You can also see that the correlation is rather volatile ranging from barely positive to about .65 which is a fairly strong positive relationship.  Volatile, but never negative, so there are no years where a bunch of below average home run hitting teams took the league by storm.

The home run environment last year was back to 81.9% of the peak in 2000, and this year’s pace is a little slower than last with home runs in 2.38% of plate appearances rather than 2013’s 2.52%, which could reduce the total home runs hit by more than 8 per team for the year, though the heat of summer will probably close that gap up some.  It is likely though that the overall home run environment will be down to the levels we saw in 2011 and 2012, and maybe the drop off from 2000 has flattened out.

Anyway, I know everyone hates a non-result, there are published papers that have been published about the bias against them even, but this is still interesting to at least me.  You always want to hit home runs, we already knew that, but the value of the home runs should not be increased in times when they are scarce and they don’t become even more necessary during a homer boom.  This means that teams shouldn’t for instance overpay for a guy like Giancarlo Stanton right now because his power bat is more valuable in the current home run environment.  It means they should overpay so that their fans can enjoy the majestic blasts and feel content knowing they will be just as valuable as ever.

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4 Responses to “Home-Run Environment And Win-Homer Correlation”

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  1. SomaDaydream says:

    “The value of the home runs should not be increased in times when they are scarce”

    This is a good point. Home runs are just a way teams score runs, and run scoring means more to a team’s success than the means by which they score runs.

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  2. Iron says:

    Nothing wrong with confirming the null hypothesis. Well done.

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  3. David says:

    Nice idea, but I dunno, I feel like this is missing something. Like you need to be comparing HRs to run scoring overall, and run scoring to wins … or something like that. As another commenter stated, home runs are just one way to score. If run scoring was up but HRs down, for example, that means it’s easier to score outside of hitting a HR and the relative value of a HR is less. The reverse also seems logical, if run scoring is down but HRs are up then the value of an HR is higher because it’s harder to score in other ways. Then, of course, your got the relation of runs scored to wins. It seems to me that there are too many other variables in play to just look at HR v. Wins and say that there is no correlation. Now, there might not be :) But I don’t know that this has demonstrated that.

    I also think you should use (Team HR / League HR) not (Team – League). You’re baking in the overall HR environment in the latter.

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    • TheRoyalTreatment says:

      No, there is a correlation as the chart shows. The correlation is “stable” across different home run environments is what I am saying.

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