THE BOOK--Playing The Percentages In Baseball

Wednesday, May 04, 2011

Overcast, with a chance of good hitting

Study:

Earned runs allowed by home pitchers were lowest on clear days at 3.93, climbing to 4.26 on cloudy days. For visiting pitchers the ERA was 4.50 in the clear and 4.68 under the clouds.
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The analysis is based on statistics from 10,758 major league day games obtained from STATS LLC and weather data collected by the National Climatic Data Center, showing the conditions at the nearest National Weather Service office to each stadium at game time. The findings are published in the current issue of the journal Weather, Climate and Society.

Kent said he had expected to see better hitting in cloudy conditions but was surprised by how strong the effect was on strikeouts. Home pitchers averaged 6.65 strikeouts on clear days, but in cloudy conditions that fell to 6.22. For visiting pitchers, the drop from clear to cloudy was from 6.14 to 5.67.
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On clear days, home teams won 56 percent of their games...When it was cloudy, that fell to 52 percent home wins…
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Home teams had 0.98 home runs per game for clear days and 0.96 when it was cloudy. For visitors, the change from clear to cloudy was from 0.95 to 1.01. Home pitchers gave up 3.37 walks on clear days and 3.43 when it was cloudy. Visiting hurlers averaged 3.56 walks for clear days and 3.50 under clouds.

Anyone who’s seen an outfielder lose a ball in the sun won’t be surprised to hear there are more errors on clear days than cloudy ones.

The difference is largest for visiting teams who would not be accustomed to the glare and light angles in someone else’s stadium. Visiting teams averaged 0.80 errors on clear days and 0.73 on cloudy days. For home teams the decline was from 0.77 on clear days to 0.75 as it got cloudier.

If someone finds the paper, please post below.