The bottom line on index funds for long-term investors
There are two ways to make money from index funds: sell the investment for a gain or earn dividends. A growth-focused index fund, like the Vanguard Growth ETF, has the potential for big gains.
However, higher rewards come with greater risk, and dividend payments will likely be minimal. If you want investment income, a dividend fund like the SPDR S&P Dividend ETF is a good choice. There's less potential for big gains, but you can earn reliable dividend income.
Although there's no single best index fund to invest in, a couple of good options are an S&P 500 index fund, which tracks about 80% of the U.S. stock market, or a total stock market fund, which tracks the entire U.S. stock market. These tend to be good choices because they're well diversified and allow you to lock in the historical growth of the domestic stock market.
All investments carry some risk, but S&P 500 index funds have historically been safe long-term investments, as the S&P 500 has delivered positive returns over long periods. The S&P 500's average annual returns are about 10%.