Toby Watson on Why Diversification Means More Than Spreading Across Asset Classes
Diversification is one of the most cited principles in investment management and one of the most frequently misunderstood — and Toby Watson brings to this subject a perspective shaped by nearly two decades of working with complex portfolios across multiple market environments.
The idea that spreading investments across different asset classes provides meaningful protection is deeply embedded in investment practice — but it is also, in many cases, incomplete. Portfolios that appear diversified at the asset class level can remain highly concentrated at the factor level, leaving investors exposed to risks they have not fully identified. Toby Watson, whose career spans structured credit, global principal funding and investment management across multiple market cycles, offers a considered perspective on what genuine diversification requires and why the conventional approach often falls short.
The Gap Between Apparent and Genuine Diversification
The most common form of portfolio diversification involves spreading capital across different asset classes — equities, bonds, real estate, commodities and so on. This approach has genuine merit. The problem arises when asset class diversification is treated as sufficient in itself — when the number of different labels applied to the assets in a portfolio is taken as an adequate measure of how diversified it actually is.
Assets in different classes can share common underlying risk factors. A portfolio holding growth equities, long-duration bonds and real estate may appear diversified across three asset classes. But if all three are sensitive to the same factor — say, the direction of interest rates — then a significant shift in that factor can produce correlated losses across the entire portfolio simultaneously. For Toby Watson, this is one of the more common ways in which apparent diversification fails to deliver the protection investors expect.
What Does Genuine Diversification Actually Require?
Genuine diversification requires understanding not just what assets a portfolio holds, but what risks it is actually exposed to. Toby Watson, whose career at Goldman Sachs gave him extensive experience of analysing risk across complex, multi-asset structures, would frame the key question as: what are the underlying factors that drive the returns of each holding, and to what degree are those factors shared across the portfolio? If multiple holdings share the same primary return driver — whether interest rate sensitivity, credit risk or economic growth — then the portfolio is concentrated in that factor regardless of how many different asset class labels are applied.
Toby Watson on Factor Diversification and Why It Matters
Factor-based thinking shifts the focus from the surface characteristics of assets to their underlying return drivers. A genuinely diversified portfolio is one in which the primary return drivers of different holdings are as independent of each other as possible — so that poor performance in one area is not systematically replicated across the rest of the portfolio at the same time.
One of the more challenging aspects of factor-based diversification is that correlations between assets tend to increase during periods of market stress. Assets that behave relatively independently during normal conditions can move together sharply when conditions deteriorate. For Toby Watson, this dynamic is particularly important because it means that diversification tends to be least effective precisely when it is needed most. A portfolio that appears well diversified based on historical correlations may offer considerably less protection than expected during a genuine market dislocation.
Geographic diversification is often cited as a straightforward way to reduce portfolio risk. In practice, however, the degree of genuine independence between geographically diversified assets has declined as global financial markets have become more integrated. For Toby Watson, geographic diversification remains useful, but it is most effective when combined with genuine factor diversification rather than treated as a substitute for it.
Liquidity Diversification — an Often Overlooked Dimension
One dimension of diversification that receives less attention than asset class or geographic spread is liquidity. Portfolios holding assets at different points on the liquidity spectrum have a genuine form of diversification that goes beyond return characteristics. Toby Watson’s experience at Goldman Sachs, working across hard asset lending and structured credit, gave him a detailed understanding of how liquidity characteristics affect portfolio behaviour — particularly during periods of market stress. For Toby Watson, ensuring that the proportion of illiquid holdings does not exceed what an investor can genuinely afford to hold through difficult periods is a basic discipline of sound portfolio construction.
Among the practical dimensions of liquidity diversification that deserve attention are:
- The distribution of assets across the liquidity spectrum — ensuring illiquid holdings remain within manageable proportions relative to the investor’s overall circumstances
- The mismatch risk between the liquidity profile of a portfolio and the potential cash needs of the investor — a mismatch that can force asset sales at unfavourable prices if not managed carefully
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Building a Portfolio That Is Diversified in Substance, Not Just Appearance
For Toby Watson, the practical implication of thinking about diversification at the factor and liquidity level requires mapping the underlying return drivers of each holding explicitly, assessing the degree to which those drivers are shared across the portfolio and making conscious decisions about which concentrations are acceptable.
Among the disciplines that tend to support genuine diversification are:
- Regular stress-testing of the portfolio against scenarios in which assumed correlations break down — assessing how the portfolio would behave if assets that normally move independently begin moving together
- A clear distinction between diversification that is genuinely structural — rooted in independent return drivers — and diversification that is superficial, based on different asset class labels applied to holdings that share the same underlying risks
Toby Watson — whose career at Goldman Sachs and subsequent work at Rampart Capital have given him a detailed view of how portfolios behave across a wide range of market conditions — would frame the central point simply: diversification is not about how many different things a portfolio holds. For Toby Watson, it is about whether those things are genuinely independent in the ways that matter most when markets are under stress — and keeping that distinction clear is one of the more important disciplines in building portfolios that are resilient in practice, not just in theory.
