His 1922 book The Trade Cycle described the "tendency for confidence to pass into errors of optimism or pessimism, " which triggers booms and busts.

FORBES: The Confidence Question

The SPX defied the odds and closed higher for the week, even though the first leg of a five-week expiration cycle has an historical tendency for stocks to trade lower.

FORBES: By Todd Salamone

In the four-year presidential cycle, the market has a strong tendency to be positive in the last two years of each presidential term.

FORBES: February Deserves Its Bearish Reputation