Week 41 Day 6: Tracking Error: How Far You Deviate From the Market

If VTI returned 12% and your diversified portfolio returned 9%, your tracking error for that year was -3%. That does not mean your portfolio was bad. It means it was DIFFERENT from VTI. Next year, your portfolio might return 14% when VTI returns 11%. Tracking error goes both ways. The more diversified you are, the more tracking error you will have -- and the more you must be prepared to tolerate it.

The tracking error challenge: (1) Tracking error is psychologically difficult. When your neighbor's VTI-only portfolio returns 15% and your diversified VTI/VXUS/BND portfolio returns 10%, you feel 5% behind. This is 'tracking error regret' -- and it causes many investors to abandon diversification at exactly the wrong time. (2) International stocks (VXUS) were the biggest source of tracking error from 2010-2024. The U.S. outperformed international stocks for nearly 15 years, creating massive tracking error for globally diversified portfolios. Many investors capitulated and went 100% U.S. stocks. If the cycle reverses (as it did in 2000-2009 when international beat U.S.), those investors will be concentrated in the underperformer. (3) Bonds create tracking error during bull markets. In strong stock markets, bonds earn 4-5% while stocks earn 15-20%. The drag from bonds is visible and frustrating. But bonds are not there to compete with stocks -- they are there to reduce drawdowns and provide rebalancing fuel. Managing tracking error: (a) Mentally benchmark against your TARGET allocation, not against 100% VTI. If your target is 60/30/10 VTI/VXUS/BND, benchmark against THAT blend, not against VTI alone. (b) Accept that underperformance relative to the S&P 500 is the COST of diversification. The benefit (lower drawdowns, less concentrated risk) is invisible until it saves you during the next crash. (c) Set a 5-year evaluation window. Tracking error over one year is noise. Over five years, diversified portfolios' risk-adjusted returns consistently justify the tracking error.

Tracking error (TE) is formally defined as the standard deviation of the difference between the portfolio return and the benchmark return: TE = sigma(R_p - R_b). For an index fund tracking its benchmark, TE should be < 0.05% (minimal). For a diversified portfolio with international and bond components, TE relative to a U.S. equity benchmark can be 5-10% or more. Tracking error aversion (Blitz, Huij, and Martens, 2011) is a well-documented behavioral bias: institutional investors (and individual investors who benchmark themselves) prefer low-TE strategies even when high-TE strategies offer superior risk-adjusted returns. This aversion to deviating from the benchmark creates a paradox: the strategies most likely to add long-term value (international diversification, value tilts, small-cap exposure) are precisely the strategies that generate the highest tracking error in the short term, leading to premature abandonment. Cremers and Petajisto (2009) introduced 'Active Share' (the fraction of a portfolio that differs from the benchmark) and showed that high-Active-Share funds (which deviate significantly from the index) outperform low-Active-Share funds (closet indexers), but only when held for 5+ years -- the short-term tracking error is the price of long-term outperformance. For individual investors, the practical lesson is: evaluate your portfolio against your personal goals (retirement readiness, income generation, drawdown capacity) rather than against the S&P 500. The S&P 500 is not YOUR benchmark; your personal financial plan is your benchmark.