Individual and team three-point field goal percentages are derived from these totals. These numbers include three-point shots made and attempted, under the same guidelines as two-point shots. "I'd be shocked if the league wasn't at least monitoring this, especially with gambling coming up, because it's an obvious factor if you're going to start gambling on how many assists a guy gets, or how many rebounds, or things of that nature," Van Bommel said.3PA-M (Three-Point Shots Made and Attempted) Fantasy sports participants already take notice of specific team biases in hopes of finding an edge, and these scoring inconsistencies could become a problem once fans can bet directly on players' numbers. This may develop into a bigger issue as the NBA gets involved with legalized sports gambling in the United States. Since franchises ultimately employ - and could therefore influence - scorekeepers, that creates a potential conflict of interest. It's common for players' performance bonuses to be tied to specific statistical benchmarks, and teams obviously use statistics and data to inform decisions on nine-figure contracts. He never heard from the league, and admits the NBA was unlikely to act on something that's ultimately inconsequential to wins and losses.īut statistical accuracy, or the lack thereof, carries real-world impact. Van Bommel suggested two ways the NBA could improve accuracy: hire an independent team of scorekeepers or establish concrete definitions for each statistic being tracked. "We have no evidence to say that the scorekeeper in this city was intentionally giving his player more assists, especially when assists are so subjective … You and I can watch a questionable assist and have completely different opinions on it," Van Bommel said. Without a clear definition of what exactly constitutes an assist, or even a block or a rebound, stats are logged at the recorder's discretion. While Van Bommel did find inconsistencies between scorekeepers, he was careful to caution that variability doesn't necessarily suggest intent. Van Bommel also tabulated which players were most affected by their scorekeepers on assists in 2015-16. The Utah Jazz scorekeeper was the stingiest, whereas the Atlanta Hawks scorekeeper was the most generous. The results showed both inflated and deflated assists totals, reflecting the subjectivity of the stat. His findings weren't as sensational as Alex's confession, but Van Bommel did calculate what he called scorekeeper generosity (how willing a team's scorekeeper was to award an assist to either team) and scorekeeper bias (how much more likely a scorekeeper was to award assists to his team). Things like how long he held the ball after the pass and how well defended he was," Van Bommel told theScore. "We looked at all the different things you would look at if you were watching film, only instead we used data. Van Bommel recorded how many plays should have been logged as assists and compared those numbers to what scorekeepers had manually entered. He crunched billions of data points using SportVU camera technology from the 2015-16 season that tracked all movement on the court. His study was later presented at the MIT Sloan Analytics Conference in 2016.
Van Bommel co-authored a paper entitled " The Van Exel Effect: Adjusting for Scorekeeper Bias in NBA Box Scores" while completing his master's degree in statistics at Simon Fraser University.
The infamous "Van Exel Game" inspired Matthew van Bommel, who works in the Sacramento Kings' analytics department, to quantify inconsistency among scorekeepers. It was a widespread practice, he said, and it benefited everyone for the numbers to pop. The scorekeeper, a man named Alex who later joined the Navy, revealed to Deadspin's Tommy Craggs in 2009 that the Van Exel game wasn't the only one where he fudged the numbers. The most egregious example of a scorekeeper going rogue came in 1997, when a disgruntled Vancouver Grizzlies employee credited Los Angeles Lakers point guard Nick Van Exel with 23 assists - one shy of Magic Johnson's Lakers record.
How much does scorekeeper bias affect the box score, why does it happen, and what's the impact of stat-stuffing? The Van Exel Game Most of the mistakes and corrections result from human error and the subjectivity of certain statistics, but there could be more at play.
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