Efficiency and productivity evaluation of basketball players' performance

Abstract

Aim: Basketball players' performances have been traditionally summarized in indices that rely on the game-related statistics (e.g. rebounds, field goals, etc). Indices are defined according to different methods (e.g. Efficiency Index - Ei, Plus-Minus, Wins Produced), seeking distinct analytic objectives. Ei is frequently used given its simplicity. However, it has questionable validity since it measures productivity instead of efficiency and uses biased calculations for scoring. This study aimed to define indices of efficiency (Basketball Efficiency Index (BEi)) and productivity (Basketball Productivity Index (BPi)) of a player's contribution to the team performance with greater validity than Ei. Methods: We gathered public NBA game-related statistics (2014/2015 - 2018/2019). We analyzed: Ei's and BEi's winning prediction accuracy; Ei's and BEi's point spread prediction accuracy; the correlation between GRS and Ei, BEi, BPi, and PER; players' rank correlation between indices. Results: In comparison to Ei, both BEi and BPi reduced the weight of points scored on the final value. Less reliance on points scored results in a more accurate comparison of the contribution of players independent of their tactical roles. Conclusion: These indices may improve coaches' understanding of the real contribution of each player to team performance.