Factor Investing

The False Bargain of Passive Investing: What the Data Actually Says

Jermaine Carter · July 27, 2026 · 7 min read

Passive index investing isn't a lie — it's an incomplete story. The evidence on costs and long-run underperformance by active managers is real and largely settled. But "just buy the index" has quietly evolved from a sound discipline into a received truth that many investors apply without examining what they're actually buying today. The S&P 500 of 2026 is not the broadly diversified proxy for the U.S. economy that it once resembled, and for clients with complex financial lives — pre-retirees, business owners, high earners with concentrated equity — accepting it uncritically may carry more risk than the conventional wisdom suggests.

The Case for Passive Is Real — and Widely Misapplied

Start with what the data actually supports. The SPIVA U.S. Scorecard, the industry's most closely tracked measurement of active versus passive outcomes, found that 79% of all active large-cap U.S. equity funds underperformed the S&P 500 in 2025 — the fourth-worst year for active large-cap managers in the 25-year history of the scorecards. Extend the lens further and the picture is even clearer: after 15 years, there were no categories in which the majority of active managers outperformed their benchmarks.

This is not a trivial finding. Costs compound. Manager selection is genuinely difficult. And the structural case for broad-market index funds — particularly in the most efficient corners of the market — is well-grounded in evidence. We don't dispute any of that.

What we do dispute is the leap from passive works well for most investors in efficient markets to passive is always the right answer, regardless of what the index actually contains. That second claim requires a closer look at the index itself.

The Index Has Changed. The Argument Hasn't.

The S&P 500 is a market-capitalization-weighted index. That means the largest companies receive the most dollars from every investor who buys in. As of mid-2026, the top 10 companies in the index account for more than 40% of its total value. That is not diversification in any traditional sense of the word.

The mechanical consequence is significant. Every dollar flowing into an S&P 500 ETF is allocated to Nvidia, Apple, Microsoft, and Amazon in proportion to their weight — not in proportion to their valuation attractiveness or earnings outlook. In one 28-session stretch between late March and early May 2026, Nomura found that just 10 stocks drove 69% of the index's gains. The other 490 companies were, largely, along for the ride.

The further concentration risk comes from correlation. Unlike past periods when the top 10 spanned unrelated industries, today's leaders are closely linked by a common theme — AI. A single macro shift in AI sentiment, capital expenditure cycles, or regulatory posture could move the top 10 in the same direction at the same time, with meaningful consequences for anyone who assumed they owned the whole economy.

History offers useful context here. In the late 1990s, technology stocks briefly commanded extraordinary weights in the run-up to the dot-com peak. Market concentration at the top is not new — but today's version is more persistent and more interconnected than prior cycles.

Where the Bargain Breaks Down for Complex Portfolios

For a 35-year-old with a long accumulation runway and no specific income requirements, concentration risk in a passive portfolio is manageable. A bad year is recoverable. The math of time is on their side.

For someone within a decade of retirement — or already drawing income from a portfolio — the calculus is different. When withdrawals are ongoing, a sharp drawdown forces the sale of holdings at depressed prices, permanently reducing the capital base that generates future income. This sequence-of-returns dynamic means the form of risk embedded in a portfolio matters enormously, not just the average long-run return.

Business owners, athletes, and high-earning professionals often arrive at the planning conversation with a separate layer of complication: concentrated positions in employer stock, equity compensation tied to a single company, or illiquid private-company stakes. Layering a passive portfolio that is itself heavily concentrated in a handful of mega-cap tech names on top of those existing exposures may compound the underlying risk rather than offset it.

Factor-based investing — systematic exposure to characteristics like value, size, profitability, and momentum — offers one evidence-grounded way to pursue broad market participation while deliberately adjusting the form of the exposure. This is not stock picking. It is structured diversification, applied with intention rather than by default. It carries its own risks and does not guarantee superior returns in any given period, but it allows a portfolio to be constructed around an investor's actual situation rather than simply mirroring whatever the largest companies happen to be at any given moment.

The Question Worth Asking

Passive investing's core insight — that costs matter, that most active managers fail to consistently add value after fees, and that staying invested is usually better than trying to time markets — remains durable. We hold that view.

But an index fund is not a neutral act. It is a decision to own the market as it is currently constituted, with whatever concentrations and correlations exist in that moment. In an environment where the top 10 stocks represent more than 40% of the S&P 500 and are largely connected by a single investment thesis, that decision deserves more deliberate examination than it typically receives.

The goal of portfolio construction is not to pick a side in an ideological debate between active and passive. It is to build a structure that reflects the investor's income needs, tax situation, existing exposures, and tolerance for specific types of risk — and then to maintain that structure with discipline over time.

Common questions

Is passive investing always the best approach?

The evidence strongly supports passive investing as a default for many investors, particularly in large-cap U.S. equities where the SPIVA data shows the majority of active managers underperform their benchmarks over long periods. However, "best" depends on what an investor is actually buying. Today's cap-weighted S&P 500 is heavily concentrated in a small number of mega-cap names, which may not suit every investor's risk profile, income needs, or existing exposures. The answer is contextual, not categorical.

What is concentration risk in an index fund, and why does it matter now?

Concentration risk refers to the outsized influence a small number of holdings can have on an index's returns. As of mid-2026, the top 10 companies in the S&P 500 account for more than 40% of the index's total value, and most of those companies share exposure to a common theme — AI investment. When top holdings move together, the diversification benefit of owning 500 names is reduced in practice. For investors near or in retirement, this matters because a concentrated drawdown may coincide with a period when they cannot afford to wait for recovery.

What is factor investing, and how is it different from traditional active management?

Factor investing is a systematic approach to portfolio construction that targets specific, research-documented characteristics — such as value, profitability, size, or momentum — rather than relying on individual stock-picking or market-timing decisions. It is transparent, rules-based, and typically lower-cost than traditional active management, while still allowing for deliberate adjustments to a portfolio's underlying exposures. Like all investment strategies, it involves risk and does not guarantee outperformance in any given period, but it offers a structured alternative to accepting a cap-weighted benchmark's current composition by default.