Betting Data Alone Cannot Identify Match Fixers in Tennis

Hours before the Australian Open started in Melbourne on Monday, a BuzzFeed-BBC investigation showed that tennis authorities hadn’t punished male pros repeatedly flagged for suspicions that they were fixing matches to maximize their or others’ betting profits. Tennis authorities quickly gathered for a news conference responding to the charges, saying they had “thoroughly investigated” any evidence.

The report provides a case study of how difficult it is to evaluate what could be suspicious betting activity. Its possible to use data analysis, to raise questions about certain matches and players.

As part of the investigation, a data reporter spent more than a year analyzing 26,000 professional men’s matches and found 15 players who lost matches with unusual betting patterns “startlingly often.”

Quickly, people wrote on social media that the data could be de-anonymized, thereby identifying the 15 players. BuzzFeed hasn’t confirmed the list of names and sent a statement by email. “The betting data we used in our analysis is publicly available — that’s how we got it,”

But using only data on betting and results to demonstrate fixing has proven problematic in other sports. “It’s very, very dangerous to make assumptions about a match being dubious because of prematch movements,” Dan Weston, a tennis analyst said in an interview.

A player could lose matches with big odds movements often without fixing matches:

A player could tank a match and deliberately lose it without fixing.

Sometimes players stand to make money by losing early in one tournament so they can get to another. Other times, players collect a bonus or appearance fee for showing up to a tournament they’d rather not play and then lose early so they can rest and focus on a bigger tournament. Deliberately losing a match is punishable by fine, but is less serious than fixing a match for gambling purposes.

Bettors could have inside information on a match outcome. For example, if the player isn’t at full strength, his coach, family members or friends might know it before betting markets do and use that knowledge or pass it on. It might not even involve an insider. In the early rounds at small tournaments, a fan who overhears a conversation or witness an injury could trade on that knowledge before anyone else in the betting markets.

Betting markets could simply get the opening odds wrong.  That typically happens when many bets are placed against the player, suggesting the initial odds were too bullish on his chances. Bookies then adjust the line to increase and balance betting volume and to reduce their exposure.

Heavy betting against the player could mean some bettors know he’s going to lose. But it could also mean that many bettors spot favorable odds for reasons that the bookmaker isn’t taking into account. Often bookmakers use an algorithm to set initial odds. Depending on how sophisticated it is, that algorithm could fail to take into account many situations. Some players are particularly tough for bookmakers to handicap, whether because they’re coming off an injury, or because they don’t play that often, or because they’re ranked higher than their true talent after a run of good luck that bettors, but not the bookmakers’ algorithms, account for.

Other betting data, video evidence and other corroborating evidence such as texts between or about players, bank records and other information would be more conclusive. BuzzFeed and other journalists don’t have ready access to this kind of data. But tennis authorities do. The Tennis Integrity Unit is using all of this information, along with tips about players suspected of fixing, and pursuing it as far as it can. It also maintains extreme secrecy around its operations, going so far as to not reveal details of its inquiries even in the rare cases when it announces a punishment.