Political disruption is the dominant risk to global economies in the current era, said Blackstone Group Inc. Chairman Steve Schwarzman.

“The conventional economic cycle doesn’t appear to be what’s the risk at this moment,” Schwarzman said in an interview with BNN Bloomberg in Toronto to be aired Thursday. “Geopolitical issues are the great unknown, which could have very substantial consequences.”

Developments in Iran, North Korea or China could upend various economies and spread, he said. “You never know which one of these things, let alone other things, that are going to happen,” he said.

Earlier in the day, Schwarzman spoke at the Canadian Club in Toronto and addressed U.S. income inequality, a key issue among Democrats running to unseat President Donald Trump in next year’s election. Candidates including Senator Elizabeth Warren have called for a steep tax on billionaires to bridge the divide between rich and poor.

“There have always been wealthy people in the U.S. but the dialogue has changed because now you have income insufficiency,” said Schwarzman, who has an estimated net worth of $17.9 billion, according to the Bloomberg Billionaires Index.

Schwarzman said the U.S. could benefit from a “very significant” increase in the federal minimum wage, perhaps double the current $7.25 an hour.

Among his other comments:

• The U.S. should invest in teachers and make them the only occupation in society that isn’t taxed. Such a move would send a signal about the importance of education and teaching in the U.S.
• Negative interest rates are “very difficult to comprehend”