Each morning, at the market’s open, Seth M. Golden, a former logistics manager at a Target store, fires up the computer in his home office in northern Florida and does what he has done for years: Put on bets that Wall Street’s index of volatility, the VIX, will keep falling.

It has been a lucrative strategy as the so-called fear gauge has been, outside of the occasional spike, largely fearless — confounding experts by sloping persistently downward and in the process making Mr. Golden a multimillionaire.

“There has been a lot of white noise,” said Mr. Golden last Tuesday on a day that the VIX plummeted more than 10 percent, allowing him to lock in profits from short trades. “You had North Korea, Afghanistan, Trump people resigning. But I was never nervous — so today I just sat back, ate some popcorn and cashed in my profits.”

On Monday, the index ticked up, after falling 8 percent on Friday, as investors took the view that the Fed would not be raising interest rates soon after a speech by Janet L. Yellen, the chairwoman of the Federal Reserve.