Investing legend Jeremy Grantham braces for 'cataclysmic declines' in stocks and shares a strategy for 'bonanza payoffs'

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• Jeremy Grantham warns of a potential stock market bubble and economic decline.
• Grantham cites falling fertility rates, climate change, and overvalued markets as concerns.
• He advises investing in green tech, sustainable resources, and efficient industry solutions.

While veteran investor Jeremy Grantham hasn't been running a portfolio for 15 years, he still monitors major themes that he thinks are important long-term and yet underrated.