Rockefeller Chairman Ruchir Sharma said every 'bubble' behind market crashes like 1929 Great Depression and financial crisis, has four Os of overvaluation, overinvestment, overleverage and overownership that define it. He said it's hard to know when AI bubble will burst but there are "some signs" of that. "Until [bubble bursts]...everyone says, 'The party is still on'," Sharma added.