Index Funds: The Evidence-Based Way to Build Wealth
Index funds track a market index like the S&P 500, giving instant diversification at minimal cost. Over 20 years, 90%+ of actively managed funds underperform a simple index fund.
What Index Funds Actually Do
An index fund buys every stock in an index — the S&P 500 index fund owns all 500 companies, weighted by market cap. When Apple is 7% of the S&P 500, 7 cents of every dollar you invest goes to Apple. No stock picking, no manager discretion, just the market.
The Cost Advantage
Vanguard's VTSAX charges 0.04% annually. A typical actively managed fund charges 0.65–1.0%. On $100,000 over 30 years at 8% returns, that expense ratio gap costs $84,000 in lost compounding. The math explains why Warren Buffett has repeatedly told his estate to put 90% in a low-cost S&P 500 index fund.
Which Index Fund to Choose
For US exposure: VTSAX (Vanguard Total Stock Market), FSKAX (Fidelity), or SWTSX (Schwab). For the S&P 500 specifically: VOO, IVV, or SPY. For global diversification: VT (Vanguard Total World). For bonds: BND. For most investors, VTSAX + a target-date fund does the job.
The Real Risk
Index funds drop when markets drop — 2022 saw the S&P 500 fall 19.4%. The risk is behavioral: investors who panic-sell lock in losses. The S&P 500 has recovered from every crash in history. Time horizon matters: index funds are for 10+ year money, not next year's car purchase.