When observing the starts of pitchers who throw many breaking pitches, simple betting strategies of wagering on these pitchers on days of relatively low air density greatly outperformed wagering on these pitchers when air density was at its highest. In each grouping in this category of pitchers, bets on starting pitchers who throw the highest percentage of breaking pitches on low air density days earned positive returns, while betting on them in the opposite case (high air density days) earned significantly negative returns. For pitchers on the other end of the distribution who throw very few breaking pitches, the opposite (and consistent) result holds true. Starting pitchers who throw very few breaking pitches earn positive returns (or lose less – depending upon group) on high rather than low air density days.
It does not appear the betting market fully encompasses the impact of air density on pitcher performance. Bets on pitchers who rely the most on their breaking pitches earn positive returns on days with low air density and take substantial losses on days where the air density is high. In contrast, pitchers who infrequently throw breaking pitches earn more (or lose less) on days with high air density compared to low air density. The betting market results are consistent with the regression results of the previous section, which showed that higher air density days lead to pitchers throwing fewer breaking pitches. High air density days led to betting market losses (poor performance) for pitchers who frequently use breaking pitches. By substituting away from the breaking ball, they may improve their performance.