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Around the middle of the 2015 season, something odd started happening in Major League Baseball (MLB): Home runs surged. They surged again in 2016 and then again in 2017. Statisticians now provide an explanation. The quality of pitching between 2015 and 2017 had gotten worse if one breaks a pitch down into measurable components and then measured pitching quality over time. Wilson called this measure ”Quality of Pitch” (QOP).