Does the 60/40 portfolio still work?

The 60/40 portfolio describes a classic allocation of investment assets: 60% is invested in equities and 40% in bonds. Equities primarily represent participation in companies and therefore return potential. In the traditional understanding, bonds are intended to provide stability, ongoing income and, in certain market phases, a counterbalance to equity risks.

The idea is not new. It is one of the best-known concepts in strategic asset allocation. It is sometimes also mentioned in connection with large institutional endowment portfolios and the so-called Yale portfolio. However, this classification should be understood with caution. For assessing the classic 60/40 portfolio, the name is less important than the logic behind it: a fixed mix of growth-oriented and more defensive building blocks is intended to enable a more balanced risk/return profile.

At first glance, this structure appears timeless. A 60% equity allocation provides participation in economic growth. A 40% bond allocation is intended to stabilise the portfolio when equity markets come under pressure. Yet this is also where the central misunderstanding lies. The allocation alone does not create genuine diversification.

Diversification only arises when the components of a portfolio actually behave differently. A bond allocation can cushion losses on the equity side only if bonds remain stable or gain in value in the relevant stress phase. If both sides lose value at the same time, the fixed allocation helps only to a limited extent.

The 60/40 portfolio should therefore not be understood merely as a simple rule of thumb. It is a portfolio idea based on certain assumptions about equities, bonds, interest rates, central bank policy and inflation. Whether it works depends on whether these assumptions still hold in the relevant market environment.

For many years, the 60/40 portfolio was able to convince investors because equities and bonds often showed a form of inverse behaviour in stress phases that was favourable for investors. When equity prices fell, economic weakness or market turbulence often led to lower interest rates. Falling interest rates, in turn, could support the prices of existing bonds.

This mechanism was particularly influential in the 2000s and thereafter. During the financial crisis in 2008, in the subsequent phase in 2009 and also during the euro crisis, bonds were able to have a balancing effect in certain stress situations. Losses on the equity side were not necessarily avoided, but they could be partly cushioned.

The technical relationship is important. When market interest rates fall, existing bonds with higher coupons become relatively more attractive. Their prices can rise. The strength of this effect depends significantly on duration. In simplified terms, duration describes how sensitive a bond or bond portfolio is to changes in interest rates.

The higher the duration, the more strongly a bond portfolio can react to interest rate movements. In an environment of falling interest rates, this can have a positive effect because bond prices can rise. In an environment of rising interest rates, however, the same mechanism works in the opposite direction. Bonds can then lose noticeable value.

The stabilising role of bonds was also supported for a long time by monetary policy. Central banks such as the ECB and the Fed were often able to respond to periods of economic weakness with interest rate cuts and further expansionary measures. This also included quantitative easing, i.e. the purchase of securities by central banks to loosen financing conditions.

For traditional balanced portfolios, this created the impression over a long period of an almost cost-free hedging component. When equity markets came under pressure, central banks often responded supportively. Falling interest rates led to gains on the bond side, which could partly offset equity losses.

However, this effect was not a guarantee. It was based on an environment in which inflation remained low and central banks had sufficient room to loosen monetary policy. As long as this environment existed, the classic equity-bond mix could appear very convincing. Once conditions changed, the assumption of stability also became more fragile.

One of the most important lessons from the development of the 60/40 portfolio is the distinction between correlation and causality. Correlation describes how two variables behave statistically in relation to one another. It shows whether they tend to move together, in opposite directions or independently of one another. Causality, by contrast, means that one variable causes the other.

In the case of the 60/40 portfolio, the earlier inverse relationship between equities and bonds was often treated as if it were a law of nature. If equities fell, bonds were expected to rise. If markets came under stress, the bond allocation was expected to stabilise the portfolio. In many historical phases, this expectation was understandable, but it was not an immutable rule.

The decisive point is this: bonds do not automatically rise just because equities fall. They can rise if the causes of equity losses lead to falling interest rates. That is a different relationship. If economic weakness prompts central banks to cut interest rates, this can be positive for bonds. If, by contrast, the pressure comes from inflation and rising interest rates, the bond allocation itself can come under pressure.

This makes clear why historical reviews should be treated with caution. They show how a portfolio worked in certain market phases. But they do not prove that the same relationships will also hold in the future. A statistical pattern can appear stable for years and still break down when the macroeconomic environment changes.

For investors, this distinction is central. Anyone who confuses correlation with causality overestimates the reliability of a fixed portfolio allocation. The question then is no longer only whether 60% equities and 40% bonds worked historically. The more important question is why they worked and whether the underlying conditions still exist today.

This is where the real depth of the 60/40 topic lies. The classic allocation is not wrong, but it is dependent. It depends on bonds actually taking on a different role from equities in stress phases. This role does not result from the allocation itself, but from interest rates, inflation, duration and monetary policy room for manoeuvre.

Inflation is the third dimension without which the 60/40 portfolio cannot be fully understood. For a long time, the focus was mainly on the relationship between equities and interest rates or between equities and bonds. But this two-dimensional picture is not sufficient when inflation becomes the driving force behind market movements.

For many years, inflation remained low even though monetary policy was highly expansionary and measures such as quantitative easing were associated with a sharp expansion of liquidity and money supply. This environment was favourable for 60/40 portfolios. Central banks could respond more supportively to economic problems without immediately being constrained by strong inflationary pressure.

In 2022, this starting point changed significantly. Inflation surged, reinforced by the energy price shock. This also changed the reaction function of central banks. Instead of cutting interest rates when markets weakened, they had to move in the opposite direction and tighten monetary policy.

For a traditional 60/40 portfolio, this constellation was particularly difficult. Equity prices fell. At the same time, interest rates rose. Rising interest rates, in turn, weighed on bonds because existing bonds can lose attractiveness when new bonds offer higher yields. The result was simultaneous pressure on both sides of the portfolio.

This moment made visible that the earlier stability relationship had not been causal. Inflation became the driving force that could weigh on both equities and bonds. It led to rising interest rates and thereby broke the correlation that many investors had long perceived as a reliable protective effect.

For the 60/40 portfolio, this is a central insight. When inflation is low, the classic allocation can tend to work well because central banks have more room to cut interest rates in periods of economic weakness. These interest rate cuts can support the bond allocation and thereby relieve pressure on the equity side.

When inflation is high, the logic is different. Central banks cannot simply loosen monetary policy, even if equity markets are falling or economic risks are increasing. They may have to raise interest rates in order to fight inflation. As a result, the bond allocation can lose its classic protective function and itself become a source of losses.

The year 2022 was therefore more than just a weak year for balanced portfolios. It was a portfolio stress test for the assumption that equities and bonds automatically react differently in difficult phases. Since then, the central question has no longer been only how strongly equities and bonds are weighted. What matters is which macroeconomic force is determining the markets.

Criticism of the 60/40 portfolio does not mean that the classic allocation has no value. It still has its place. There are market phases in which it can work well. Particularly in an environment of low inflation and falling interest rates, the bond allocation can once again play a stronger stabilising role.

What is problematic, however, is the idea that 60% equities and 40% bonds represent a universally valid formula for a successful investment strategy. A rigid allocation may not sufficiently take into account that inflation, the level of interest rates, correlations and monetary policy conditions change over time.

Modern portfolio positioning should therefore examine more closely which parameters are currently decisive. This includes inflation as well as interest rate risk in the bond allocation. Duration also plays an important role because it determines how sensitive the portfolio is to rising or falling interest rates.

Equally important is the question of how dependent the portfolio is on the classic equity-bond correlation. If the stability of a portfolio depends essentially on bonds rising when equities fall, then this assumption needs to be questioned regularly. It may hold in some phases, but fail in others.

A more flexible portfolio positioning can be useful here. Flexibility does not mean investing arbitrarily or abandoning fixed rules entirely. It means adapting the composition of the portfolio more strongly to changing conditions and not relying solely on a historical standard allocation.

This also includes looking beyond equities and bonds. Capital markets consist of more than these two building blocks. Precious metals, absolute return strategies or selected investment niches can take on additional roles in a portfolio if they are used carefully. However, they should not be understood as automatic solutions.

Such building blocks can help reduce dependence on a single correlation assumption. Here too, however, the interaction is decisive. An additional asset class does not automatically improve a portfolio. It must fit the portfolio management approach and be able to make a plausible contribution in different market phases.

The most important consequence is therefore this: the fixed allocation is not the real core of successful portfolio positioning. The real core is the ability to assess the framework conditions correctly. A 60/40 portfolio can be sensible if its stability assumptions hold. If they do not, a rigidly maintained allocation can show significant weaknesses.

The 60/40 portfolio still works, but not automatically. It is not a universal formula for success and not a guarantee of stability. Its effect depends critically on whether equities and bonds actually react differently in the relevant market environment.

Historically, the classic mix was particularly convincing when inflation was low and central banks were able to cut interest rates in stress phases. Falling interest rates could support the bond allocation and partly cushion equity losses. In such phases, the 60/40 portfolio appeared to be a robust and simple solution.

However, the year 2022 showed that this effect cannot be taken for granted. When inflation rises, central banks raise interest rates and equities come under pressure at the same time, classic equity-bond diversification can fail. In that case, not only the 60% equity allocation loses value; the 40% bond allocation can also come under pressure.

The central insight is therefore this: the 60/40 portfolio has its place, but it is dependent on correlation. This correlation must not be confused with a causal relationship. Anyone assessing the classic allocation should therefore look not only at the allocation, but also at inflation, interest rate developments, duration, central bank policy and the actual interaction between the portfolio building blocks.

A flexible portfolio positioning can help reduce rigid dependencies. This does not mean that equities and bonds lose their importance. It means that their role should be reviewed again and again in the current environment. That is precisely the difference between a historical standard solution and contemporary portfolio management.