There’s a new pitching stat in the Team Statistics Tables. It’s called HR/Fly, and it’s basically the number of home runs given up by each team per each flyball allowed.
Research published by Ron Shandler’s Baseball Forecaster has shown that about 10% of all flyballs are hit for home runs, once you correct for ballpark. In fact, the Forecaster folks found that flyball rates are the best predicter of home runs allowed.
So, if a team allows significantly more or less than 10%, you can expect that rate to “regress to the mean” of 10% over a full year.
Take a look at the table. The Twins have allowed 16% of flyballs to fall for home runs; I expect that rate to decline. On the other hand, only 6% of the Rangers’ fly balls allowed have been home runs (adjusted for ballpark). That number will rise.
We’ll keep track of this stat throughout the year to see what really happens.
One other thing: we use the three-year home run park factors published by BIS in the Bill James Handbook. If we were to use home run park factors for just this year, you might notice the 0.054 factor at Shea Stadium. There have been 32 home runs hit in Mets’ games this year, but only one of them at Shea.