The Bogleheads 4 Fund Portfolio is globally diversified across stocks and bonds. Here we’ll investigate its components, historical performance, and the best ETF’s to use in its implementation.
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What is the Bogleheads 4 Fund Portfolio?
The Bogleheads 4 Fund Portfolio is simply the Bogleheads 3 Fund Portfolio with the addition of international bonds. The theory and mechanics underlying the composition of the 4 Fund Portfolio is the same as that of the 3 Fund Portfolio. For the sake of brevity in this post, I won’t be repeating it here. I would strongly encourage you to go read the post on the 3 Fund Portfolio first and then come back here where I’m simply discussing the addition of the international bonds component.
The Bogleheads 4 Fund Portfolio, as the name suggests, is comprised of 4 funds capturing U.S. stocks, U.S. bonds, international stocks, and international bonds. This gets you fully diversified globally across all styles and cap sizes for stocks and bonds. Let’s look at the specific assets.
At global market weights, U.S. stocks only comprise about 50% of the global market. International stocks don’t move in perfect lockstep with U.S. stocks, offering a diversification benefit. If U.S. stocks are declining, international stocks may be doing well, and vice versa.
During the period 1970 to 2008, an equity portfolio of 80% U.S. stocks and 20% international stocks had higher general and risk-adjusted returns than a 100% U.S. stock portfolio. I choose to allocate 20% to international stocks in my portfolio. Just as in the 3 Fund Portfolio, here I’ve set both international stocks and international bonds at 1/3 the allocations of their domestic counterparts.
The inclusion of international bonds in diversified portfolios and target date funds is a fairly recent occurrence. Until recently, costs of international bond fund products were prohibitive for retail investors, and international assets of all kinds were viewed with skepticism until about the 1990’s. Vanguard didn’t begin including international bonds in their target date funds until 2013.
The evidence seems to show that international bonds may offer a small diversification benefit in terms of credit risk on the fixed income side due to their low correlation with both U.S. stocks and U.S. bonds, but there’s no compelling reason to think it’s any significant benefit. This potential diversification benefit is even less convincing for a portfolio that is not bond-heavy.
The infamous Larry Swedroe suggests, based on a 2012 Vanguard paper, that investing in foreign bonds may be prudent for reducing portfolio volatility if and only if the investor can do so with low fees and with currency hedging to eliminate currency risk. Without currency hedging, it’s basically FOREX trading. Luckily, Vanguard’s Total International Bond ETF (BNDX) satisfies those requirements.
Vanguard published another paper in 2018, proposing that “various local market risk factors (such as interest rates, inflation, and yield curves) have resulted in relatively low correlations of government bond yields across markets over the past 50 years, suggesting a diversification benefit to increasing the number of global markets in a fixed income allocation.” While the research is comprehensive, the tiny diversification benefit they illustrate is negligible in my opinion. Specifically, they showed that for a 60/40 portfolio during the period 1985-2013, diversifying internationally with fixed income resulted in a reduction of volatility as measured by standard deviation from 9.5 to 9.4, a reduction of 1%.
In short, there’s no good reason to consciously avoid international bonds, but there’s also no good reason to embrace them either; it’s unlikely to help your portfolio, and it’s unlikely to hurt it.
Assuming a retirement age of 60, my general rule of thumb is to use [age-20] for bond allocation, obviously titrating up or down based on risk tolerance. Vanguard has a useful tool here to help you choose. You can also view how different allocations have performed historically.
Given that, for the sake of simplicity in this post, let’s assume a starting age of 20 and a retirement age of 60, yielding an average investor age of 40. Based on that, a one-size-fits-most 80/20 allocation for the Bogleheads 4 Fund Portfolio is:
- 60% U.S. Stocks
- 20% International Stocks
- 15% U.S. Bonds
- 5% International Bonds
Bogleheads 4 Fund Portfolio Portfolio Historical Performance
My data for the total international bond market only goes back to 1999, so the backtest below is for the period 1999-2019, comparing an 80/20 Bogleheads 4 Fund Portfolio to the S&P 500 index.
Given the short time period, CAGR’s are almost identical, with the 4 Fund Portfolio having a higher risk-adjusted return from lower volatility and smaller drawdowns:
Bogleheads 4 Fund Portfolio ETF Pie for M1 Finance
M1 Finance is a great choice of broker to implement the Bogleheads 4 Fund Portfolio because it makes regular rebalancing seamless and easy, has zero transaction fees, allows fractional shares, and incorporates dynamic rebalancing for new deposits.
Using entirely low-cost Vanguard funds, we can construct an 80/20 allocation of the Bogleheads 4 Fund Portfolio pie like this:
- VTI – 60%
- VXUS – 20%
- BND – 15%
- BNDX – 5%
You can add the this pie to your portfolio on M1 Finance by clicking this link and then clicking “Save to my account.”
Disclosure: I am long VTI and VXUS.
Disclaimer: While I love diving into investing-related data and playing around with backtests, I am in no way a certified expert. I have no formal financial education. I am not a financial advisor, portfolio manager, or accountant. This is not financial advice, investing advice, or tax advice. The information contained in the investing-themed posts on this website is for informational and recreational purposes only. Read my lengthier disclaimer here.