Could S&P 500 ETFs Alone Fund Your Entire Retirement?

Most investors have heard that investing in the S&P 500 (SNPINDEX: ^GSPC) is one of the best ways to create long-term wealth. It's probably the default option in their workplace retirement plan. Even a lot of self-directed investors will put their money in the Vanguard S&P 500 ETF (NYSEMKT: VOO) or the iShares Core S&P 500 ETF (NYSEMKT: IVV) and call it a day. There's a reason, after all, that these are the two largest ETFs in the world, with more than $1.6 trillion in assets combined.

The S&P 500 is many people's only investment. That can create some problems because it leaves a whole slew of asset classes unrepresented. Including them can enhance growth opportunities, mitigate downside risk, or create a regular income stream. Without any of that to complement it, the high tech concentration or the growth tilt of the index could mean too much volatility.

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Key takeaways

• The S&P 500 has delivered a roughly 10% average annual return over the long term, making it a more than adequate core retirement holding.
• The top 10 holdings account for around 38% of the index. That makes it concentrated and heavily exposed to a handful of tech stocks.
• Holding just the S&P 500 means you're excluding small caps, international stocks, fixed income, gold, and crypto. These asset classes offer important diversification benefits.
• An S&P 500 ETF is sufficient as a core portfolio holding, but retirement portfolios should have more balance.

The case for owning only the S&P 500

It would be easy to look at the returns of the S&P 500 over the past 10 to 15 years and come to the conclusion that it's the only investment you need. Thanks to its heavy concentration in the "Magnificent Seven" stocks, it has outperformed most sectors, styles, and themes over that time.

But setting aside the performance numbers, the S&P 500 includes many of the best companies the U.S. economy has to offer. It owns companies such as Apple, Microsoft, Amazon, Walmart, JPMorgan Chase, ExxonMobil, Johnson & Johnson, and Visa. These companies produce billions of dollars in cash flow, generate huge revenues, and have been around for decades. They're the cornerstones of the economy and will likely be around for many more decades.

These are exactly the kinds of high-quality companies that can make a great portfolio.

The case for owning more than the S&P 500

While the S&P 500 is unquestionably a great index to invest in, it's also incomplete.

Here's what investors are missing out on by investing only in the S&P 500:

• Small and mid caps: The Vanguard Total Stock Market ETF (NYSEMKT: VTI), which invests in the entire U.S. equity market, holds about 3,500 stocks. The 3,000 stocks not held by the S&P 500 represent about 25% of the entire U.S. equity market capitalization. Small and mid caps have an entirely different sector allocation and cyclical exposure. Omitting them means missing out on a big chunk of the U.S. economy.
• International stocks: As we've seen over the past year, foreign stocks can perform very well when U.S. stocks stall. They, too, have a different economic composition and are sensitive to different factors than U.S. companies.
• Fixed income: Bonds may be boring, but they can balance out portfolio risk and provide an important income component. As workers get closer to retirement, relying more on fixed income for safety and income becomes more important.
• Gold: Precious metals typically perform well during inflationary periods and geopolitical disturbances. They traditionally have a very low correlation to stocks, which makes them a great risk reducer.
• Crypto: Bitcoin and other stablecoins have become a legitimate asset class. Adding crypto as even a small piece of a broader asset allocation makes some sense.

Holding more than just U.S. large-cap stocks lets you participate in different market cycles, helps smooth out overall portfolio volatility, and can help build a portfolio more suited to your goals and risk tolerance.

Investors should own more than just the S&P 500

The S&P 500 is a great core investment, but you need more.

I'm a big advocate of diversification and looking for ways to mitigate risk exposure. Adding different asset classes helps accomplish this. In most cases, it's not about trying to pick winners. Simply buy the global economy and let the long-term power of compounding do the work for you.

JPMorgan Chase is an advertising partner of Motley Fool Money. David Dierking has positions in Apple and Vanguard Total Stock Market ETF. The Motley Fool has positions in and recommends Amazon, Apple, JPMorgan Chase, Microsoft, Vanguard S&P 500 ETF, Vanguard Total Stock Market ETF, Visa, and Walmart and is short shares of Apple. The Motley Fool recommends Johnson & Johnson. The Motley Fool has a disclosure policy.