Diversifying a real asset portfolio in unreal times
Owning a variety of investments can create a reassuring impression of diversification. Different assets serve diverse purposes, respond to disparate incentives, and generate returns in distinct ways.
Beneath those differences, they may share vulnerabilities that become apparent only when economic conditions change.
A portfolio can appear diversified on paper while remaining heavily exposed to a handful of forces that influence nearly everything the investor owns.
When different investments depend on the same conditions
Diversification works by combining investments whose returns don't move in perfect unison. The less closely their returns are correlated, the greater their potential to offset one another's losses.
The challenge is that asset classes don't always behave independently simply because they're classified differently.
Consider a portfolio containing equities, corporate bonds, and commercial real estate. Each represents a different type of investment, but all three can benefit from the same economic environment:
- Low borrowing costs.
- Readily available credit.
- Strong business activity.
When those conditions reverse, their vulnerabilities may become apparent simultaneously.
Source: Bank for International Settlements[1]
Why rising interest rates can hurt more than bonds
Bonds are particularly sensitive to changes in interest rates. Generally, when market yields rise, existing fixed-rate bonds decline in price.
The same increase in borrowing costs can affect assets that appear unrelated to fixed-income investments.
Higher interest rates can reduce the present value of expected corporate earnings and put downward pressure on equity valuations. They can also increase financing costs for property owners and make commercial real estate less attractive relative to investments offering higher yields.
The Federal Reserve's research on monetary policy transmission documents how interest rates influence financial conditions and asset valuations[2].
The result is a portfolio containing several asset classes that may all depend, to varying degrees, on relatively inexpensive capital.
Investors may have diversified their holdings without diversifying their exposure to interest rates.
What happens when correlations stop cooperating?
Historical relationships between asset classes can provide useful information about diversification, but those relationships aren't fixed.
During periods of financial stress, investments that ordinarily behave differently can begin moving in the same direction. The 2022 market downturn offered a particularly visible example.
Scatter plot of rolling 12m returns: SPX and UST when both are negative (monthly,1973-2024)[3]
As inflation accelerated and central banks tightened monetary policy, both U.S. equities and Treasury bonds suffered substantial losses. The traditional expectation that bonds would cushion equity declines proved unreliable during that period.
When inflation becomes a dominant economic concern, stocks and bonds can become more positively correlated, weakening their ability to offset each other's losses[4].
A portfolio's diversification benefits depend partly on the economic environment in which they're needed.
The concentration that asset allocation percentages can't reveal
A portfolio might allocate 40% to equities, 30% to bonds, 20% to real estate, and 10% to alternatives.
Those percentages describe where capital is invested, not the underlying risks.
If several holdings respond negatively to tightening credit conditions, their combined exposure could be considerably larger than any individual allocation suggests.
Institutional investors sometimes examine portfolios through risk factors rather than asset-class labels. These factors include sensitivity to economic growth, inflation, interest rates, and other conditions that influence returns across different markets.
Common risk factors can influence asset prices across different markets, which can create shared vulnerabilities among seemingly unrelated investments[5].
Source: Pacific Investment Management Company LLC[6]
This perspective reveals why adding another asset class doesn't automatically introduce an independent source of risk or return.
Diversification is more complicated than counting assets
The number of investments in a portfolio provides only a partial picture of its diversification.
What matters is how those investments respond to changing conditions, particularly when the economic assumptions supporting their valuations begin to break down.
No portfolio can eliminate uncertainty, and correlations can change precisely when people rely on them most.
A portfolio's apparent variety may conceal substantial exposure to the same economic forces.
Perhaps the true measure of diversification lies in how many independent sources of risk a portfolio contains, rather than the number of assets an investor owns.
In a conversation with The Gold Exchange Podcast, John Rubino explores why preserving wealth in an unpredictable financial environment requires thinking beyond conventional asset allocations.
Sources:
https://www.bis.org/publications/aer-2025/financial-conditions-changing-global-financial-system
- https://www.federalreserve.gov/monetarypolicy/monetary-policy-what-are-its-goals-how-does-it-work.htm
- https://www.bankofsingapore.com/research/bonds-remain-a-perennial-diversifier.html
- https://www.imf.org/en/blogs/articles/2026/02/18/stock-bond-diversification-offers-less-protection-from-market-selloffs
- https://www.aqr.com/-/media/AQR/Documents/Alternative-Thinking/AQR-Alternative-Thinking---Broad-Strategic-Asset-Allocation.pdf
- https://www.pimco.com/us/en/resources/education/understanding-risk-factor-diversification