But now Arnold Ventures, the foundation founded by the Arnolds, is going after an unsuspecting cause: sports betting. The foundation announced Tuesday it has awarded roughly $2.6 million in new research grants to 12 universities and think tanks studying the fast-growing sports betting industry. 

The main motivation is figuring out what online sports betting is doing to the people who use it. The projects, which are housed at institutions including Princeton University, the University of Pennsylvania, and the University of Wisconsin, will examine how gambling affects financial well-being, household formation, mental health, and consumer behavior—and, in some cases, what policymakers can do to reduce harm.

Arnold Ventures is seeking a stronger evidence base to give policymakers more information and “better tools” to make decisions about sports betting legislation, a foundation spokeswoman told Fortune. 

“Sports betting expanded rapidly across the country, yet policymakers often lack rigorous causal research on its effects and on which regulatory approaches are most effective,” she said. “These studies are designed to help fill that gap.”

The grants, first reported by CNBC, reflect Arnold’s growing conviction that betting has fundamentally changed since a 2018 Supreme Court decision opened the door to legalization. 

“Being able to bet over the phone has dramatically increased access and lowered friction,” Arnold, a former Enron analyst who eventually started a hedge fund, told CNBC. “You can bet on every pitch. You can bet with a speed that was never possible when you had to place a call to put a bet down.”

Justin Milner, Arnold Ventures’ executive vice president of evidence and evaluation, framed the funding as a way to arm lawmakers with independent data: “Anyone with a smartphone could effectively have a casino in their pocket.”

Why the research skips prediction markets

Notably, none of the 12 studies will examine prediction markets such as Kalshi and Polymarket. The Arnold Ventures spokeswoman told Fortune the omission is a matter of research design: “Access to betting data from prediction market platforms is extremely limited,” she said, “which makes it challenging for independent researchers to conduct rigorous causal evaluations.”

Most of the funded studies instead compare states based on when they legalized online sports betting, an approach that lets researchers isolate the effect of those decisions. Prediction markets, regulated federally by the Commodity Futures Trading Commission, offer no comparable state-by-state variation, she explained. 

“A lot of states jumped into legalizing sports betting in 2018. And I think that they were very attracted to the potential tax revenue,” Arnold told CNBC. “It’s very appealing for a state legislature to get money from a voluntary tax rather than a mandatory tax.”

Asked whether Arnold Ventures views any single argument—financial harm, mental health, athlete integrity, or disappointing tax revenue—as its most persuasive with legislators, the spokeswoman said the foundation doesn’t “approach the issue through a single lens.” 

The goal, she said, is to ensure “policymakers understand the full range of consequences associated with sports betting, so that when they are ready to act, the evidence is there to support them.” She added the foundation is not funding the work “to support a predetermined legislative outcome or position on legalization.”

A track record of giving it away

These award announcements are just a drop in the bucket of the Arnolds’ broader philanthropy. The couple has donated half of their net worth.

According to a 2025 Institute for Policy Studies report, they’re the only Giving Pledge signers who are technically in compliance with the pledge’s promise to give away at least half of one’s wealth. 

Fellow billionaires like Melinda French Gates have openly criticized other Giving Pledge signers for not doing enough.

“Have they given enough? No,” French Gates said in an interview with Wired published in late 2025.