POINTWISE: Predicting Points and Valuing Decisions in Real Time with NBA Optical Tracking Data

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How can we evaluate an NBA player’s decision making? Certainly, we can consider whether he takes high-percentage shots or turns the ball over, but how do we evaluate his drive that collapsed the defense, or his decision to shoot a contested shot instead of making the extra pass? The vast majority of traditional and advanced NBA metrics rely on only a small subset of the actions that comprise a basketball possession: shots, assists, rebounds, and turnovers. In doing so, many players’ contributions are overlooked (e.g. passes that aren’t assists, or dribble penetrations that don’t end in layups/dunks) or overvalued (sinking a contested mid-range shot when a teammate was open for a corner three).

Pointwise introduces a new foundation for quantitative decision analysis in the NBA based on “expected possession value”, or EPV. By analyzing players’ tendencies using optical tracking data, we assign a point value to every instant of every NBA possession by computing the number of points the offense is expected to score by the end of that possession. EPV acts like a stock ticker, responding continuously to players’ movement and decision-making. Using EPV, we can assess the quality of every on-ball decision a player makes by how much he increased or decreased the value of the possession for his team. EPV thus opens up new avenues of basketball analysis that focus on decision-making, opportunity creation and prevention, and optimal responses that were not possible before—in short, a new microeconomics for the NBA.

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