There are plenty of advantages in using exchange-traded funds (ETFs) to fill gaps in an investment portfolio, and lots of investors mix and match ETFs with mutual funds and individual stocks and bonds in their accounts. But it's equally possible to build a complete portfolio out of nothing but ETFs, which in most cases, track indexes. In this article, we’ll discuss the benefits and trade-offs of an ETF-only portfolio using index ETFs. (While actively managed ETFs do exist, in this article an all-ETF portfolio refers specifically to using index ETFs only.)
How can you tell if an all-ETF portfolio makes sense for you? For the most part, it comes down to what your goals are—and your preferences. As a general rule, ETFs provide excellent diversification at a low ongoing expense ratio (OER) since many are passive funds that track a certain benchmark index. Because of this, they typically offer transparency—it’s easy to see what stocks, bonds, or other investments the ETF holds each day. If these are top characteristics you look for in your investments, owning nothing but ETFs may be a straightforward yet flexible solution worth a closer look.
There are some trade-offs to think through. An all-ETF portfolio means giving up actively managed mutual funds, which have the potential to outperform index ETFs through professional selection of stocks and bonds. You'll also leave behind the control that comes with a portfolio composed solely of individual securities you have selected. Some people won’t want to give these things up, even though these approaches have specific disadvantages as well (see table below).
A portfolio of index mutual funds, meanwhile, would be very similar to an all- ETF portfolio with two main exceptions: ETFs trade differently than index mutual funds, and for certain niche asset classes, you can find ETFs but very few or no index mutual funds.
Pros and cons of four types of portfolios relative to each other
Actively managed mutual funds
Index mutual funds
All-Index ETF portfolio
Individual stocks and bonds
If you think an all-ETF portfolio might suit you, here are three ways to build one, ranging from ultra-simple to very fine-tuned.
1. Keeping it simple
One option you can consider would be using two ETFs to help provide a balanced, diversified portfolio of stocks and bonds:
- A total world stock market ETF
- A total bond market ETF
For instance, if you're an investor seeking moderate risk and decide that you want 60% of your portfolio in stocks and 40% in bonds, you could consider purchasing an all-country stock index ETF and then combine it with a bond ETF.
World stock market ETFs may track an index like the Morgan Stanley Capital International All Country World IndexSM (MSCI ACWI), which provides exposure to U.S. stocks, developed-market international stocks and emerging-market international stocks.
Some bond ETFs track the broad Bloomberg Barclays US Aggregate Bond Index, which covers:
- Treasury bonds
- Government-agency bonds
- Mortgage-backed bonds
- Investment-grade corporate bonds
- Some dollar-denominated international bonds
The advantage of this type of portfolio is its simplicity: one stock fund and one bond fund. It will be easy to see when you need to rebalance. Plus, because ETFs trade intraday and generally cost part of the bid-ask spread every time you buy or sell, a two-ETF portfolio can help keep your trading costs low.
One disadvantage of this portfolio is that it’s not very fine-tuned. For instance, as of March 31, 2021, MSCI ACWI had about 58% in U.S. stocks and 42% in non-US stocks, according to Morgan Stanley Capital International. If you prefer to have a larger allocation to U.S. stocks, for example, you might want two separate stock ETFs.
Another drawback to this portfolio is that it lacks any allocation to Treasury Inflation Protected Securities (TIPS), sub-investment grade bonds (also known as high yield or junk bonds), and non-dollar-denominated international bonds, not to mention other asset classes such as commodities and real estate. Additional asset classes can help further diversify your portfolio. Still, if simplicity is what you seek, the two-ETF portfolio can be an alternative worth considering.
2. Middle of the road
An intermediate approach to an all-ETF portfolio could consist of about 10 ETFs.
For stocks, you could have:
- A large-cap U.S. ETF
- A small-cap U.S. ETF
- An international developed-market ETF
- An emerging-market ETF
For bonds, you could start with the same core bond ETF described above and diversify further by including ETFs that invest in:
- Sub-investment grade ("high-yield" or "junk") bonds
- International bonds
The advantage of this portfolio can help provide balance. It has enough ETFs to give you coverage of more asset classes and the ability to adjust your portfolio weights in most areas, but not so many funds that it becomes too challenging to keep track. The disadvantage of this portfolio is that it offers neither maximum simplicity nor maximum customizability.
On the other end of the spectrum from an ultra-simple ETF portfolio is a fine-tuned portfolio with 20 or more ETFs. This type of portfolio can make sense for investors who like to allocate their accounts toward exactly the parts of the market they expect to perform best.
This portfolio begins similarly to the middle-of-the-road ETF portfolio but then divides the various parts into thinner slices:
- U.S. large-cap stocks can be divided into sectors such as financials and health care, or even narrower industries such as banks and biotech.
- The U.S. stock allocation can further be divided to include mid-cap or micro-cap stocks, or styles such as growth and value.
- The international stock allocation can be adjusted to include international small-cap stocks in regions, such as Europe and Asia or in individual countries like Germany and China.
The core bond index can be broken into its components:
- Agency-backed bonds
- Mortgage-backed securities
- Corporate bonds
The average maturity of the bonds in the portfolio can be fine-tuned to include more long-term bonds or short-term bonds.
- Agricultural commodities
- Base metals
Real estate ETFs can be added to the portfolio and could even be split into U.S. and global.
With the fine-tuned portfolio, it’s unlikely that you would want to hold every possible ETF at the same time. For instance, rather than holding allocations to all 11 stock sectors and every individual country possible, you would likely have core allocations to certain ETFs, and then add weight to the ETFs representing only those sectors or countries that appear most attractive.
The advantage of this portfolio is the ability to get almost exactly the exposure you want to each narrow piece of the market while still enjoying the diversification that ETFs offer over individual stocks and bonds.
The disadvantages are complexity and trading costs. With so many ETFs in the portfolio, it’s important to be able to keep track of what you own at all times. You could easily lose sight of your total allocation to stocks if you hold 13 different stock ETFs instead of one or even five. In addition, with so many ETFs in the portfolio and relatively more buying and selling, the impact of bid-ask spreads could add up quickly.