Massachusetts senator Elizabeth Warren and former vice president Joe Biden have an equal chance of being the Democratic nominee for the 2020 US presidential election, according to PredictIt, a political-prediction betting market run by Victoria University of Wellington, New Zealand.

Volume jumped on Warren bets over the 24 hours leading up to the first Democratic primary debate on Wednesday, from 4,000 to 8,000 trades. The senator’s chances were priced at $0.21 just 24 hours ago, and rose to $0.24 during the debate, settling at $0.22 by the end. Biden, who was trading at $0.26 a day ago, hit a high of $0.27 before dropping back down to $0.24. The higher the price, the more likely the outcome.

As of this writing, New Jersey senator Cory Booker’s chances were trading at $0.05 to Hawaii senator Tulsi Gabbard’s $0.04. Former Texas congressman Beto O’Rourke was equal with Gabbard at $0.04. That’s a penny more than former San Antonio, Texas mayor and Housing and Urban Development secretary Julian Castro, at $0.03, and two cents higher than Minnesota senator Amy Klobuchar and New York City mayor Bill de Blasio, both at $0.02.

At the bottom of the pile were California congressman Eric Swalwell, former Maryland congressman John Delaney, and Ohio congressman Tim Ryan, at $0.01 each. Others who gamblers believe have the same chance of becoming the Democratic nominee include movie star and former pro wrestler Dwayne “The Rock” Johnson, Facebook founder Mark Zuckerberg, and Oprah Winfrey.

Some advise to take the betting markets’ signals with a grain of salt. When a sportsbook sets odds on anything from a football game to a presidential election, the goal is to ensure bettors lay an equal amount of money on either side of the proposition, explained Sacha Paruk, lead oddsmaker for gambling analysis site SportsBettingDime.com. In other words, it’s a reflection of what the house believes will reduce its own risk, rather than a pure prediction of a particular result.

Paruk points out how wrong the betting markets were on the 2016 US presidential election.

“I do recall that president Trump was a very long shot to win the last election,” he said, “and quite a few people lost substantial amounts of money betting on Hillary Clinton.”