“There are not more than five musical notes, yet the combinations of these five give rise to more melodies than can ever be heard.”
Sun Tzu, The Art of War
Note: None of the material or content contained herein constitutes investment advice. It is solely for educational and informational purposes. Past performance is not an indicator of future performance.
In The Art of War, Sun Tzu observed:
There are not more than five musical notes, yet the combinations of them give rise to more melodies than can ever be heard.
In the equity markets, the fundamental drivers of a company’s value are similarly limited - revenue growth, margin expansion, free cash flow generation, capital return, and competitive advantage. Yet, from these basic elements, the financial industry has engineered tens of thousands of mutual funds, smart-beta ETFs, and complex portfolio strategies.
For decades, we have been sold the idea that to be “safe” investors, we must own every colour, taste, and note simultaneously. We call this diversification. But as the structure of public markets rapidly shifts, it is time to ask a difficult question: Is broad equity diversification actually protecting us, or is it just diluting the upside?
The Case For Diversification: The Only “Free Lunch”
The consensus view, rooted in Harry Markowitz’s Modern Portfolio Theory, is that diversification is the only “free lunch” in investing. The premise is mathematically sound: by combining equities that do not move in perfect lockstep, you can reduce the volatility of your portfolio without necessarily sacrificing expected returns.
Mitigating Idiosyncratic Risk: No matter how deep your research, individual companies are vulnerable to unpredictable shocks - accounting scandals (see our upcoming book club conversation), abrupt regulatory changes, or sudden technological obsolescence. Holding 30+ stocks ensures that a catastrophic failure in one business doesn’t wipe out your portfolio.
Capturing Market Beta: Broad diversification ensures you participate in the long-term upward drift of human progress and corporate profitability.
Behavioural Protection: Highly concentrated portfolios are volatile. Even if a concentrated portfolio outperforms over a ten-year horizon, the violent drawdowns along the way often cause investors to panic and sell at the exact wrong time. Diversification, in theory, smooths the ride, keeping you in the seat.
The Case Against Diversification: Protecting Against Ignorance
The counter-argument, championed by legendary investors like Warren Buffett and Peter Lynch, is that extreme diversification is simply a hedge against not knowing what you are doing.
“Diworsification”: If you have done the rigorous work to identify five truly exceptional businesses with wide moats and excellent management, why would you allocate capital to your 40th or 50th best idea? Every stock you add beyond your highest-conviction ideas dilutes your overall return.
Diluting Your Edge: In the equity market, alpha (market-beating returns) is a zero-sum game. If you hold 200 stocks, your portfolio closely mirrors the benchmark. By definition, you cannot beat the market if you *are* the market.
The Attention Deficit: A portfolio manager can deeply understand the mechanics, threats, and opportunities of 15 to 20 businesses. Nobody can intimately track the micro-economics of 150 companies.
What the Latest Research is Saying vs. The Consensus
The consensus heavily favours passive, broad-market index investing - buying the whole haystack. But recent academic research and modern market dynamics paint a more nuanced, disruptive picture of *why* markets behave the way they do.
The cornerstone of modern equity research is Hendrik Bessembinder’s landmark study, which revealed a brutal power law: just 4% of publicly traded companies account for all of the net wealth creation in the stock market above Treasury bills since 1926. The other 96% of stocks, collectively, were dead weight.
How this is interpreted depends entirely on what game you are playing and what level you are playing it at. If you have an informational or analytical edge, true wealth is generated by avoiding the dead weight, not buying it.
Why the Industry is Set Up This Way
If concentration is required for outsized returns, why does the average actively managed mutual fund hold over 50 stocks? The answer lies in the structural realities of the asset management industry.
1. Career Risk and “Tracking Error”
John Maynard Keynes famously noted that it is better for a reputation to fail conventionally than to succeed unconventionally. In the institutional world, portfolio managers are judged against a benchmark (like the S&P500). If a concentrated manager is wrong and underperforms the benchmark by 15%, they lose their job. If a highly diversified manager closely hugs the benchmark and underperforms by 1.5%, they get a bonus. The industry optimizes for career survival, which mandates looking exactly like the crowd.
2. The Asset Gathering Machine
Asset management is a business of scale. Firms get paid a percentage of Assets Under Management (AUM). If a brilliant manager runs a concentrated portfolio of 15 mid-cap stocks, the strategy has strict capacity limits - if they manage too much money, they end up owning too much of the underlying companies, destroying their liquidity. To manage $50 billion, a fund *must* buy hundreds of stocks. They are diversifying not because it makes for a better portfolio, but because it is the only way to absorb more fee-paying capital.
3. Closet Indexing
Many active funds are essentially “closet indexers.” They charge active management fees but hold so many equities at weightings so close to the benchmark that they mathematically cannot justify their cost. They sell the illusion of active oversight while hiding behind the safety of extreme diversification.
The Verdict
Ultimately, determining your stance on diversification requires profound self-awareness.
If your goal is capital preservation, market-average compounding, and peace of mind, broad equity diversification is a beautiful tool. But if you are seeking genuine capital accumulation and market-beating returns, you have to acknowledge the math: alpha requires taking a differentiated stance. You cannot paint a masterpiece by blindly mixing all the colours together - you just end up with grey.