Batting Average (AVG) and On-Base Percentage (OBP) are two of the most commonly cited statistics in baseball. Existing research has demonstrated that for a team, OBP is more closely correlated to runs scored than is AVG, and secondly, for players, OBP is more closely correlated over time than is AVG. We offer an algebraic explanation for the latter phenomenon. Specifically, we will prove that batting average depends more heavily upon a particularly unpredictable variable, hits per balls in play (HPBP), than does OBP. This result will explain why for both batters and pitchers, on-base percentage is a better indicator of future performance than batting average.
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