Investor Warren Buffett’s right-hand man says the U.S. stock market is overvalued, but he doesn’t know when the bubble will burst. Billionaire Charlie Munger is a vice chairman at Buffett’s Berkshire Hathaway conglomerate. Munger said Wednesday that the recent frenzy over GameStop’s stock was driven by small investors gambling on the stock market. He says the investors are playing the stock market like bettors at a horse rate. Munger says inexperienced investors are being lured into the market by newer brokerages like Robinhood that offer commission-free trading. In a lighter moment, Munger also said the secret to a happy life is low expectations.