According to CoinMeta, despite the strong performance of the U.S. stock market in recent years, many investors are feeling anxious. With concerns about the high valuations of tech stocks, the sustainability of the boom in artificial intelligence (AI), and rising interest rates, a sell-off could occur at any time. If a bear market does emerge in 2026, investors might consider selling their stocks and shifting to cash. Nevertheless, long-term investors need not worry too much about a bear market, as having a diversified stock portfolio is generally the best way to build wealth. For long-term investors, the S&P 500 index is a worthwhile option to consider. This index is one of the most popular in the world, managing over $1 trillion in investor assets, and has had an average annual return of 15.04% over the past decade.