Bonus Episode: Michael Philbrick - Skis and Bikes: The Untold Story of Diversification

Episode Summary

Executive Summary: This bonus episode features Mike Philbrick reading his chapter on diversification from The Best Investment Writing, Volume 2. Using the “skis and bikes” analogy, he argues that true diversification comes from combining uncorrelated return streams with different risk profiles and economic sensitivities, not merely owning many assets. He shows how balanced, multi-asset portfolios can reduce volatility and drawdowns while improving long-term risk-adjusted returns.

Main Topics: Book and episode introduction (Priority: 3/5): The host introduces the new volume of The Best Investment Writing, highlights its 41 curated articles, and notes that author proceeds support charities chosen by the writers. Skis and bikes analogy (Priority: 5/5): Philbrick explains diversification through a seasonal business example: skis sell in winter and bikes in summer, stabilizing revenue by combining complementary, non-overlapping sources of demand. Why diversification works (Priority: 5/5): He argues that diversified portfolios reduce variability without eliminating return because investors can hold multiple risky assets that earn returns at different times for different reasons. Diversification in theory (Priority: 5/5): Using two hypothetical uncorrelated markets and a five-asset example, he shows that combining assets can preserve expected return while reducing volatility and peak-to-trough losses. Why traditional balanced portfolios fail (Priority: 5/5): He contends that 50/50 stock-bond portfolios are often not truly balanced because stocks dominate risk, leaving bonds unable to provide much real diversification in crises. Diversification in practice and risk parity (Priority: 4/5): Philbrick compares global equities and a broader asset universe, arguing that meaningful diversification requires looking beyond stocks to assets sensitive to different growth and inflation regimes, with risk parity as a practical implementation.

Key Arguments: Diversification is not about owning many assets; it is about combining assets with low correlation and different economic drivers. Assets that move in different directions can still both add value over time, just as skis and bikes do in different seasons. Investors seeking higher returns must accept risk; diversification helps reduce portfolio risk without forcing a wholesale move into low-return cash or bonds. Traditional balanced funds are often misnamed because stock volatility dominates the portfolio, making bonds ineffective as diversification ballast. Owning many stocks or stock funds does not provide true diversification because they share the same primary risk factor: growth expectations. Global equity markets have become more correlated over time, limiting diversification benefits within equities alone. A truly diversified portfolio should include assets that perform in different inflation and growth environments, such as government bonds, TIPS, commodities, REITs, and gold. Risk parity improves diversification by balancing risk contributions across assets, which can improve returns when portfolios are scaled to the same volatility target.

Data Points: Number of selected investment articles in Volume 2: 41 - The host says the second volume expands to 41 hand-selected articles. Stock/bond portfolio loss during financial crisis: 33% peak-to-trough loss - A 50/50 U.S. stocks and high-grade bonds portfolio during 2008-2009. Average correlation of equally weighted stock-bond portfolio with stocks: 0.91 - The portfolio is described as almost perfectly correlated with stocks most of the time. Lowest rolling 3-year correlation since 1993: Never below 0.8 - For the equally weighted U.S. stocks and bonds portfolio versus stocks. Average volatility of individual ACWI constituent markets: 26.4% - Annualized volatility across the major global equity markets examined. Volatility of equally weighted global equity portfolio: 19.8% - Used to calculate the diversification ratio for global equities. Global equity diversification ratio: 1.33x - 26.4% divided by 19.8%, described as a 33% diversification advantage. Average pairwise correlation among global equity markets: about 0.6 - Over the past 26 years, correlations among global equity markets are reported as elevated. Weighted average volatility of equally weighted global asset classes: 17.1% - Benchmark for the broader diversified asset universe. Volatility of equally weighted portfolio of global asset classes: 9.9% - Demonstrates stronger diversification across asset classes than within equities. Diversification ratio of equally weighted global asset-class portfolio: 1.73 - 17.1% weighted average volatility divided by 9.9% portfolio volatility. Weighted average volatility of global risk parity portfolio assets: 13.65% - Reflects heavier bond weighting in the risk parity construction. Volatility of global risk parity portfolio: 6.5% - Used to show the diversification benefit in a risk parity framework. Diversification ratio of global risk parity portfolio: 2.1 - 13.65% divided by 6.5%. Target volatility used to compare strategies: 10% - Both the global 60-40 and risk parity portfolios were scaled to the same risk level. Expected compound return in hypothetical example: 10% per year - Used in the theoretical illustration of uncorrelated markets and five assets. Hypothetical market volatility: 20% - Used in the theoretical five-asset diversification example. Maximum peak-to-trough loss in Market 1: 26% - Hypothetical uncorrelated market example. Maximum peak-to-trough loss in Market 2: 34% - Hypothetical uncorrelated market example. Loss reduction from diversification in two-market example: 40% smaller peak-to-trough loss - The diversified portfolio had a smaller drawdown than either single-market portfolio. Volatility reduction in two-market example: About one-third less volatility - Diversified portfolio versus concentrated portfolios.

Pivotal Quotes: "The most fundamental principle of investing is diversification. But in our experience, few investors understand what diversification means." — Mike Philbrick: Opening of the chapter, establishing the central thesis. "The magic of diversification is that it allows investors to keep more of their money invested in higher-risk assets with commensurately higher expected returns while lowering the overall risk of the portfolio." — Mike Philbrick: Explains why diversification matters for long-term investing. "Traditional balanced portfolios are not balanced at all." — Mike Philbrick: Critique of 50/50 stock-bond portfolios and their risk concentration.

Implications: Listeners should rethink diversification as risk balancing across uncorrelated economic drivers, not simple asset count. For portfolio construction, broader cross-asset diversification and risk parity may improve resilience and long-term outcomes.