Predictable Long-term Stock Market Booms and Busts?

Do stock markets following predictable long boom and bust periods? In the August 2024 draft of their paper entitled “The Anatomy of Lost Stock Market Decades”, Todd Feldman and Brian Yang examine the regularity/frequency of bull periods (strong gains) and lost periods (no gains) of at least 10 years. They also test two metrics to identify when the S&P 500 Index is in a bull or lost period: (1) the ratio of the S&P 500 Index level to a dividend discount model (DDM) valuation of the index; and, (2) an exponential cumulative loss metric calibrated via a 20-year moving average (weighting recent losses more than older losses to sharpen regime shift detection). Using monthly stock market levels from Global Financial Data for the U.S., Canada, Japan, Australia, Germany and France and Robert Schiller’s data for the S&P Composite Index from the 1800s through 2023, they find that:

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