Systematic risk: The PRIME forces that move markets

Diversifying your portfolio is the investing equivalent of eating your vegetables—it’s simple, sensible, and almost always good for you. Diversification broadens your potential return sources and reduces the risk of relying too heavily on any single investment. But diversification can only go so far. It can help with asset concentration risks, but certain macroeconomic forces move markets in ways that diversification simply can’t sidestep.

Financial experts have narrowed these risks down to five forces: purchasing power, reinvestment rate, interest rate, market, and exchange rate—neatly summarized in the acronym PRIME.

As a long-term investor, you will be exposed to these PRIME risks, whether you hold stocks, bonds, real estate, or interest-bearing cash equivalents. So understanding what they are, where they come from, and what diversification can and can’t do is a crucial part of building a resilient investment strategy.

A deeper dive into PRIME

PRIME is made up of five macroeconomic forces whose risks can’t be “diversified away” using traditional means of portfolio diversification, such as holding equities across sectors or using bonds and fixed-income assets to balance out equity exposure.

What makes these risks hard to escape is that they’re built into the financial system itself. If you own stocks, bonds, or even cash-like assets, you’re exposed to at least one of them.

Purchasing power risk

What is it?

Purchasing power risk, often called inflation risk, is the risk that your money loses value (e.g., buys less) over time as prices rise. When inflation outpaces your returns, the real (inflation-adjusted) value of your cash, income, and investments gets eroded, even if your account balances appear to grow.

Purchasing power risk affects everyone, but it tends to hit cash holders and conservative savers the hardest. Money sitting in the bank steadily loses value during periods of rising prices. Inflation also erodes the real value of wages and income from interest-bearing assets.

What can you do?

To help offset purchasing power risk, consider:

• Inflation-resistant assets. Stocks, real assets (such as real estate, metals, and commodities), or inflation-linked securities like Series I savings bonds (“I bonds”) can help you keep pace with inflation.
• Stocks for the long term. Over long periods, stocks have historically provided stronger inflation-adjusted returns than cash or bonds.

Reinvestment rate risk

What is it?

Reinvestment rate risk (or simply “reinvestment risk”) is the risk that any cash flow from an investment—coupon payments, interest income, or the principal returned when a bond or certificate of deposit (CD) matures—has to be reinvested at a lower rate later on. When rates fall, the future income you can earn on those proceeds shrinks.

Reinvestment rate risk shows up when the economy shifts into a lower-rate environment. Investors who rely on steady interest income—particularly retirees and conservative savers—will feel it most.

What can you do?

To reduce the impact of reinvestment rate risk, you can stagger the maturities of your bonds or CDs—often called a bond ladder—so your principal doesn’t all come due at once. You can also mix shorter- and longer-term fixed-income holdings to spread out when cash flows return to you. These approaches help you manage when you have to reinvest, even though they can’t fully protect you from shifts in the broader rate environment.

Interest rate risk

What is it?

When a central bank such as the Federal Reserve raises interest rates, it can put pressure on asset prices—stocks, bonds, and some alternative assets. While reinvestment risk affects future interest income, interest rate risk can have an immediate effect on the current value of your investments.

For bonds, higher rates cause bond prices to fall, even though their coupon payments haven’t changed. For stocks, higher interest rates raise borrowing costs, which can squeeze corporate earnings and limit a company’s ability to invest and expand. Higher rates reduce the present value of future earnings, making stocks—especially growth-oriented companies—less attractive relative to other investments.

What can you do?

On the bond side, you can diversify by holding a mix of short- and longer-term bonds. Longer-duration bonds are more sensitive to rate changes, so spreading your exposure across different maturity dates helps smooth out the impact when rates move. For stocks, you can diversify across styles—growth, value, and different sectors—that may react differently to changes in borrowing costs. And holding some cash keeps your portfolio liquid and gives you flexibility during volatile rate cycles.

Market risk

What is it?

Market risk refers to the risk that a broad stock market decline will pull down many, if not all, your investments at the same time. No matter how diversified your portfolio may be, a sharp drop in investor sentiment, geopolitical shocks, and even recessions and earnings cycles can trigger market-wide declines, causing most assets to fall as one.

What can you do?

When markets suddenly shift to “risk-off” mode, particularly in a panic-induced environment, it can be a tough situation to manage. As a long-term investor, you can take some comfort in the power of dollar cost averaging to give you more bang for your investing buck during bear markets. Advanced traders often employ hedging strategies such as protective put options, short positions in futures on stock indexes, or inverse ETFs.

Exchange rate risk

What is it?

Exchange rate risk is the risk encountered when your investments are tied to the value of foreign currencies or markets. If you invest in foreign securities, or if you hold shares in U.S. companies that rely on international markets for their sales or supply chain, currency movements can boost or reduce returns, regardless of how the underlying investment performs.

What can you do?

You can soften the impact of exchange rate risk by keeping a diverse mix of domestic and international assets in your portfolio so you’re not exposed to just one currency. You might also consider investing in currency-hedged funds, which can help reduce the impact of exchange rates on returns. Direct currency hedging is complex, expensive, and generally not recommended unless you’re experienced in foreign exchange markets.

The bottom line

Every investment portfolio carries PRIME risk. Because these risks extend far beyond the idiosyncratic risks of individual companies and sectors, you can’t diversify them away. They’re embedded in the underlying forces that move entire markets.

However, understanding PRIME risk helps you identify what you’re exposed to—and why. Although you can’t eliminate systematic risk, you can manage it. A long-term perspective, periodic rebalancing, careful position sizing, and realistic expectations can help you navigate periods when these risks intensify instead of reacting to them after the fact.