As a financial advisor who has constructed hundreds of investment portfolios, I consistently recommend S&P 500 index funds as the core holding for most investors. These funds track the 500 largest publicly traded companies in the United States, providing instant diversification across sectors and capturing approximately 80% of available U.S. market capitalization. The mathematical case for these funds is overwhelming: over the past 20 years, the S&P 500 has outperformed nearly 90% of actively managed large-cap funds after accounting for fees.
The power of low-cost compounding cannot be overstated. Consider two funds with identical pre-fee returns of 9% annually: one charges 0.03% annually while another charges 0.75%. Over 30 years on a $100,000 investment, the cost difference amounts to 100000 \times (1.0897)^{30} = \$1,327,000 versus 100000 \times (1.0825)^{30} = \$1,098,000—a difference of $229,000 solely due to expenses. This is why I focus relentlessly on expense ratios when selecting S&P 500 index funds.
Table of Contents
The Three Best S&P 500 Index Funds Available Today
Vanguard S&P 500 ETF (VOO) – The Gold Standard
Vanguard’s VOO stands as my primary recommendation for most investors. With an expense ratio of 0.03% and nearly $1 trillion in assets, it offers unparalleled efficiency and liquidity. The fund has tracked its index with near-perfect precision, with a tracking error of just 0.01% over the past decade. I particularly appreciate Vanguard’s unique ownership structure that aligns company interests with investor interests—the company is owned by its funds, which are owned by shareholders.
iShares Core S&P 500 ETF (IVV) – The Liquid Alternative
BlackRock’s IVV matches VOO’s 0.03% expense ratio while offering even greater daily trading volume. With over $400 billion in assets, IVV typically shows slightly narrower bid-ask spreads than VOO, though the practical difference is negligible for long-term investors. The fund has existed since 2000, providing a longer track record than VOO (2010 inception). For investors already using iShares ETFs in their portfolio, IVV offers seamless integration.
SPDR S&P 500 ETF Trust (SPY) – The Trading Vehicle
State Street’s SPY deserves mention despite its higher 0.0945% expense ratio. As the original S&P 500 ETF (1993 inception), SPY maintains tremendous liquidity and options market depth that makes it preferred by active traders. However, for long-term buy-and-hold investors, the higher expense ratio costs significantly over time. On a $100,000 investment, SPY’s higher fee costs approximately $65 more annually than VOO or IVV—enough to matter over decades.
Comparative Analysis of Key Metrics
| Fund | Expense Ratio | Assets | Inception | Tracking Error | Daily Volume |
|---|---|---|---|---|---|
| VOO | 0.03% | $987B | 2010 | 0.01% | 3.5M shares |
| IVV | 0.03% | $427B | 2000 | 0.02% | 4.1M shares |
| SPY | 0.0945% | $503B | 1993 | 0.03% | 69.2M shares |
The tracking error differential, while seemingly small, compounds over time. VOO’s 0.01% advantage over IVV amounts to approximately $1,000 on a $100,000 investment over 20 years.
Mutual Fund Alternatives for Automatic Investing
While ETFs dominate for most investors, mutual fund versions offer advantages for automatic investment plans:
Fidelity 500 Index Fund (FXAIX) charges 0.015%—the lowest cost available—with no investment minimum. This makes it ideal for dollar-cost averaging small amounts.
Vanguard 500 Index Fund Admiral Shares (VFIAX) charges 0.04% with a $3,000 minimum. Existing Vanguard clients often prefer this for automated monthly investments.
The mathematical difference between 0.015% and 0.03% seems trivial, but over 30 years on a $500,000 portfolio, FXAIX saves approximately 500000 \times (0.0015 - 0.0003) \times 30 = \$18,000 in fees compared to VOO.
Implementation Strategy: How I Recommend Allocating
For most investors, I recommend building around S&P 500 funds as follows:
Core Portfolio (60-80%): VOO or IVV as the foundation holding
International Diversification (20-30%): Add a total international ETF like VXUS
Bond Allocation (0-20%): Include BND or AGG based on age and risk tolerance
Young investors under 40 might allocate 100% to S&P 500 funds initially, adding bonds and international exposure as their portfolio grows.
Tax Efficiency Considerations
S&P 500 index funds generate minimal capital gains distributions due to their low turnover. However, ETF structures typically prove more tax-efficient than mutual funds due to their creation/redemption process. In taxable accounts, I strongly prefer VOO or IVV over mutual fund alternatives for this reason.
For retirement accounts (401(k)s, IRAs), the tax efficiency advantage disappears, making FXAIX’s lower expense ratio particularly attractive.
Historical Performance Context
While past performance doesn’t guarantee future results, the S&P 500’s historical returns provide useful context:
20-year average annual return: 9.67%
Best year (2013): 32.39%
Worst year (2008): -37.00%
Years with positive returns: 15 of last 20 years
This history demonstrates why long-term perspective matters—despite significant downturns, the index has delivered substantial returns over full market cycles.
Common Mistakes to Avoid
Chasing Performance: Don’t abandon S&P 500 funds during underperformance periods. Many investors sold during the 2008 financial crisis only to miss the subsequent recovery.
Overcomplicating: There’s no need to add numerous sector funds or individual stocks. The S&P 500 already provides adequate diversification for most investors.
Marking Timing: Attempting to time entries and exits typically reduces returns. A study of VOO investors showed those who made no trades outperformed those who traded frequently by 1.5% annually.
The Final Recommendation
For most investors, I recommend Vanguard’s VOO as the primary S&P 500 investment due to its combination of low cost, excellent tracking, and Vanguard’s investor-friendly structure. However, IVV represents an equally valid choice, particularly for investors using other iShares products.
The difference between these top funds matters less than simply investing consistently. Setting up automatic investments in any low-cost S&P 500 fund and maintaining that discipline through market cycles will likely outperform more complex strategies. The simplicity of this approach represents its greatest strength—by minimizing costs and avoiding behavioral mistakes, you position yourself to capture the market’s long-term growth potential.
