Last week, we updated our mid-May analysis of park factors based on granular batted-ball data, showing the offense-inflating impact that a hot summer can have, especially in certain parts of the country. This week, let’s take a look at the season-to-date overall and fly-ball park factors for all 30 parks, one league at a time, focusing on some interesting park-specific information.
First, here’s the quick-and-dirty on the method used to calculate these park factors. Through August 21, 106,962 balls were put into play during MLB regular-season contests. They resulted in an overall batting average of .328 and slugging percentage of .537, while fly balls generated a .328 AVG and .895 SLG. Line drives generated a .661 AVG and .872 SLG, and ground balls a .237 AVG and .258 SLG. (Oh, and pop ups have generated a .018 AVG and .028 SLG.) Each BIP type was split into “buckets” separated by 5-mph increments. The top fly-ball bucket begins at 105 mph, and the top liner and grounder buckets begin at 110 mph.
For each ballpark, the actual production derived from that park’s actual BIP mix was compared to the projected production, assuming that each BIP bucket generated MLB average production for that BIP type/exit-speed combination. Convert everything to run values, and voila, park factors, both overall and by BIP type.
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