USF Study Links Sportsbook Promotions to Sharp Rise in Parlay Betting

TAMPA, Fla. – A USF-led study found parlay betting rose sharply during the years sportsbook promotions expanded.

By 2023, parlay wager and stake shares were about 19 percentage points above the 2018-2020 reference period. The researchers analyzed approximately 547 million NFL wagers placed with a large regulated U.S. sportsbook between 2018 and 2023.

The study was written by Richard Borghesi, a finance professor at the University of South Florida, Steven Salaga of the University of Georgia and Michael Mondello of USF.

Parlay Use Remained Elevated Without Promotional Wagers

The peer-reviewed study, published in the Journal of Gambling Studies, examined the period when sportsbook bonuses, free bets and profit boosts first appeared in the dataset. Bonuses were introduced in 2021, followed by free bets in 2022 and profit boosts in 2023, while parlay use increased across the same period.

The rise was not limited to wagers placed directly through those offers. After researchers excluded promotional wagers, parlay wager and stake shares remained about 17 percentage points above the 2018-2020 reference period.

The authors stop short of saying promotions caused the shift. Instead, the findings show that promotional periods coincided with substantial growth in parlay use and suggest that assessments of sportsbook incentives should consider changes in the types of bets customers choose, not only wagering volume.

Related Research Shows Shift Toward Parlays

A related paper published in Finance Research Letters in September examined the same 547 million-wager dataset from another angle. It found that parlays increased from 33.59% of NFL wagers in 2018 to 72.51% in 2023.

Same-game parlays, which were absent from the 2018 data, accounted for 32.05% of wagers by 2023. Traditional parlays represented another 40.46%, meaning multi-leg bets had become the majority of wagers in the dataset.

Borghesi and Mondello are based in USF’s Muma College of Business, while Salaga is affiliated with the University of Georgia. The related research found that the shift toward parlays occurred within existing bettors as well as through changes in the wider customer base.

Greater parlay use was also associated with higher bettor losses when wagering volume and total stake were held constant. Multi-leg wagers generally produce higher sportsbook margins than single-leg bets, making changes in bet selection relevant to both consumer outcomes and operator revenue.

Findings Add to Debate over Gambling Promotions

The USF findings come as researchers and regulators place greater attention on how gambling incentives influence player behavior. A separate state-funded UNLV promotions study is examining whether sportsbook bonuses and odds boosts can contribute to problem gambling in Colorado.

The two projects address different questions. The USF research uses transaction data to measure how betting choices changed as promotions expanded, while the UNLV project is designed to investigate whether promotional offers can directly contribute to gambling harm.

The USF study does not examine online casino bonuses, so its findings should not automatically be applied to casino play. Online casinos nevertheless use their own promotional incentives, including bonus credits and deposit offers, making the broader question of how promotions affect gambling behavior relevant across the industry.

For regulators, the research suggests that evaluating promotions may require looking beyond how much customers wager. Changes in the types of bets customers choose, particularly movement toward multi-leg products such as parlays, could also become part of the wider consumer-protection debate.

RELATED TOPICS: Responsible Gambling