The optimal level of diversification is the maximum you can achieve at a very low cost. Investors should stop diversifying when the marginal benefit is outweighed by significantly higher fees, such as moving from broad market ETFs (3bps) to private equity (400bps).
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Historically, private equity was pursued for its potential outperformance (alpha). Today, with shrinking public markets, its main value is providing diversification and access to a growing universe of private companies that are no longer available on public exchanges. This makes it a core portfolio completion tool.
In your 40s, resist diversifying into areas you don't understand. Instead, invest 70% of your capital into your core area of expertise where you have an information advantage. Allocate 20% to adjacent opportunities and only 10% to "moonshot" ventures outside your competency.
The primary decision-makers for mass-market 401(k) plans are often HR or finance teams, not investors. To shield their companies from employee lawsuits, they have historically prioritized funds with the lowest fees, creating a massive structural barrier for higher-fee alternative investments to gain traction.
The dominance of low-cost index funds means active managers cannot compete in liquid, efficient markets. Survival depends on creating strategies in areas Vanguard can't easily replicate, such as illiquid micro-caps, niche geographies, or complex sectors that require specialized data and analysis.
Private equity's low reported correlation with public markets is largely an illusion created by smoothed, infrequent valuations ("volatility laundering"). The effect is exaggerated when institutions report private asset returns with a one-quarter lag, creating "accounting diversification" instead of real risk reduction.
Vanguard's first index fund had a ~2% expense ratio (180 bps), far from today's near-zero fees. This historical fact shows that for innovative financial products, low costs are an outcome of achieving massive scale, not a viable starting point. Early fees must be high enough to build a sustainable business.
BlackRock's CIO of Global Fixed Income argues that unlike equities, fixed income is about consistently getting paid back. The optimal strategy is broad diversification—tilting odds slightly in your favor and repeating it—rather than making concentrated, high-conviction "bravado" bets on specific market segments.
The increased volatility and shorter defensibility windows in the AI era challenge traditional VC portfolio construction. The logical response to this heightened risk is greater diversification. This implies that early-stage funds may need to be larger to support more investments or write smaller checks into more companies.
Market efficiency increases with company size and liquidity. Therefore, the excess returns (alpha) from investment factors like value are significantly larger in the inefficient micro-cap space. For large-caps, the market is so efficient that factor premiums are minimal, making low-cost indexing a superior strategy.
The sign of a working diversification strategy is having something in your portfolio that you're unhappy with. Chasing winners by selling the laggard is a common mistake that leads to buying high and selling low. The discomfort of holding an underperformer is proof the strategy is functioning as intended, not that it's failing.
