More than 11% of the world’s more than 2,000 billionaires have run for election or become politicians, according to a study highlighting the growing power and influence of the super-wealthy.

While billionaires have had mixed success at the ballot box in the U.S., billionaires around the world have a “strong track record” of winning elections and “lean to the Right ideologically,” said the study, which is by three professors at Northwestern University.

“Billionaire politicians are a shockingly common phenomenon,” the study said. “The concentration of massive wealth in the hands of a tiny elite has understandably caused many observers to worry that the ‘super-rich have super-sized political influence.’”