S&P 500 vs Total Stock Market: Does the Difference Actually Matter?

The S&P 500 (VOO, IVV, SPY) holds the 500 largest US companies. The Total Stock Market (VTI, FSKAX) holds ~4,000 US companies, including mid-cap and small-cap stocks. Their historical returns differ by less than 0.5% annually over 20 years. For most long-term investors, the choice between them is the least important investment decision you'll make — but the difference does matter in specific scenarios.