The mainstream media often discusses the stock market with a short-term mindset. Even worse, pundits often promote market-timing strategies. They draw arbitrary lines on charts to explain when it's time to buy or sell, and it often sounds very sophisticated. But the data is clear: Market-timing strategies are prone to failure.

After analyzing how the S&P 500 (SNPINDEX: ^GSPC) performed in the first 10 months of 2024, Goldman Sachs analysts wrote, "While investors may want to wait for a better entry point, we believe that the potential benefit of investing, even at an inopportune time, outweighs the downside of not investing at all."

Time in the market (not timing the market) is what matters. Indeed, one of the worst mistakes investors could have made in 2024 was to sit on the sidelines. Read on to learn more.

While valuations have been elevated throughout 2024, investors who avoided the stock market have likely paid a very high price. Consider three hypothetical portfolios with money in an S&P 500 index fund. All three had $10,000 invested at the beginning of this year, but their strategies differed thereafter.

It's natural to assume Portfolio 2 performed best because the investor had perfect timing. It's also natural to assume Portfolio 3 performed worst because the investor had the worst possible timing. But only one of those assumptions is correct. Listed below are the values of the hypothetical portfolios after the first 10 months of 2024.

Clearly, avoiding the stock market in 2024 could have been very costly. Portfolio 2 is worth $585 more than Portfolio 3, so perfect timing offered a small benefit versus the worst timing. But both did better than Portfolio 1. The owner of that portfolio made about half as much money as the other two investors because they were always waiting for a better opportunity.

Bears often sound smart when explaining why the stock market is due for a correction, but attempting to time a market correction is a great way to miss out on gains. Famous investor Peter Lynch once warned that "far more money has been lost by investors preparing for corrections, or trying to anticipate corrections, than has been lost in corrections themselves."