A 16th-century proverb advises: "It's unwise to sell a bear's skin before catching it."
That's one of the stories used to explain why, in modern times, Wall Street types call someone who sells a stock expecting its price to drop a "bear." It follows that a market in which securities or commodities are persistently declining in value is known as a "bear market," like the one U.S. stocks are experiencing now.
When assets are steadily rising over a period of time, it is known as a "bull market."
In my money and banking classes, I teach students about the efficient market hypothesis, which states that stock prices are rational, in that they are always fairly priced based on available information. But when there are big swings in the stock market, it's hard for my students and others to resist using more emotive terms like "bulls" and "bears," which call to mind the "animal spirits" of investing.
So how do you know when you're in a bear market?
The Securities and Exchange Control Commission defines a bear market as a period of at least two months when a broad market — measured by an index such as the Standard & Poor's 500 (S&P 500) — falls by 20 percent or more. When it rises by 20 percent or more over two months or more, it is a bull market. The S&P 500 index, which includes most of the most well-known U.S. companies, has declined about 24 percent since its peak Jan. 3, 2022.
Not everyone strictly follows this two-month rule. For example, in March 2020, when the S&P 500 plunged 34 percent in a matter of weeks due to the onset of the COVID-19 pandemic, many analysts still called it a "bear market."
A milder form of a bear market is "correction." During a correction, prices drop by 10 to 20 percent from the previous peak.
Some analysts estimate there have been 26 bear markets in the S&P 500 since 1928, excluding the one that began in 2022. The average length was 289 days, with a decline of about 36 percent in value. The longest was in 1973-74, which lasted 630 days.
There have been fewer bull markets — 24 since 1928. They tend to last a lot longer, though, often for multiple years.