The stock market has 70% chance of crashing in a few years as there's a bubble forming in asset prices on the verge of implosion, legendary investor and GMO's Co-founder Jeremy Grantham said. "I'm only interested in...really great bubbles...like 1929, 2000 and 2021...three senior bubbles in...US stock market. We've checked off pretty well every one of the boxes," he said.