The Average S&P 500 Bear Market Has Lasted 340 Days. Here's Why History Says That's Good News for Investors.

The S&P 500 (SNPINDEX: ^GSPC) has been riding a bull market for about four years now, and there's little indicating that it will end soon.

Still, some investors are worried about a potential artificial intelligence stock bubble, and nearly half of S&P 500 stocks are already in bear market territory.

When a full-blown bear market comes along, it lasts an average of 340 days, according to Yardeni Research.

Nearly a year's worth of extended S&P 500 declines is a lot to stomach, but the good news for investors is that bull markets last much longer, and the average upside far outweighs the average bear market decline.

That means riding out one year of bear market losses to tap into long-term gains is worth the price.

Image source: Getty Images.

The bear market's silver lining

Research from Charles Schwab shows that since 1966, the average S&P 500 bear market has lasted about 15 months and resulted in a 38% decline. So most investors are looking at about a year of declines or more, with substantial losses.

But the silver lining is that bull markets last an average of five to six years.

That means bull markets last up to 6 times as long as bear markets on average.

Not only do they last longer, but the average gain of a bull market -- 210% -- far outweighs the average bear market's decline of 38%.

Achieving those long-term gains is certainly worth the short-term pain, but it's easier said than done.

It's impossible to miss out on a bull market if you do this

Your gut instinct during a prolonged bear market will likely be to take your money out of your portfolio and put it somewhere safe.

And no one will blame you for doing this because, of course, your stocks are on the decline, and everyone else will be selling theirs as well.

But selling all your stocks during a bear market is a big mistake.

Research from JPMorgan Chase shows that between March 2005 and March 2025, seven of the 10 best days in the market occurred within two weeks of the 10 worst days. The best potential for huge stock gains usually follows the worst days.

Here's why that matters for your portfolio: Missing those seven best days would have cut your 20-year returns in half compared to staying invested.

The investment bank's research showed that a $10,000 portfolio invested during that period would be worth $70,000 if it had taken advantage of the seven best days in the market. But if it had missed those days, the same portfolio would have dropped to less than $35,000.

Keeping your money in the market won't be easy when the daily financial news services are all reporting significant share price declines, with more on the way.

But for investors who keep their money in the S&P 500 -- and even buy stocks at discounted prices -- the long-term upside far outweighs the short-term pain of the bear market. And that's very good news for investors.

Charles Schwab is an advertising partner of Motley Fool Money. JPMorgan Chase is an advertising partner of Motley Fool Money. Chris Neiger has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends JPMorgan Chase. The Motley Fool recommends Charles Schwab and recommends the following options: short September 2026 $95 calls on Charles Schwab. The Motley Fool has a disclosure policy.