Today’s Lead-Lag Report post is sponsored by Evoke

The future is highly uncertain, with potential challenges in growth, inflation, and geopolitics, making diversification crucial.

Most investors are unknowingly underdiversified. A traditional 60/40 portfolio is 98% correlated to the stock market, potentially exposing investors to more risk than they realize. The S&P 500 historically experienced extended periods of underperformance, including:

1. Underperforming cash from 1966 to 1982 during inflationary times

2. A 0% average return from 1929 to 1949

3. A lost decade prior to the recent 15-year bull market

Historical bear markets often started with high valuations. Given current high valuations, we may be on the verge of another challenging period for U.S. equities.

Risk parity seeks to offer a more diversified allocation than conventional mixes. By spreading risk across global equities, Treasuries, TIPS, and commodity producers and gold, investors can maintain a low-cost, tax-efficient passive mix seeking:

1. Equity-like long-term expected returns

2. Lower risk than stocks

3. Reduced risk of a lost decade

To learn more about the RPAR Risk Parity ETF, visit rparetf.com.

The Passive Trap: Why Index Concentration Is a Liquidity Time Bomb

Mechanical inflows made the largest weights the market. The same mechanics run in reverse, and no one is standing on the other side.

MICHAEL A. GAYED, CFA

AUG 27, 2026

KEY HIGHLIGHTS

• The ten largest S&P 500 companies still carry roughly 37 to 40 percent of index weight depending on methodology, down modestly from the 40.7 percent year-end peak but still historically extreme.
• Vanguard's VOO has taken in roughly 70 to 80 billion dollars so far in 2026, about half its record 2025 pace, even as US-listed ETFs overall crossed 1 trillion dollars in first-half inflows for the first time.
• Active large-cap managers remain 723 basis points underweight the Magnificent Seven as of the first quarter of 2026, a gap that has widened rather than closed since late 2025.
• This is not a valuation call. It is a market-structure observation about who sets the price and who is left when flows reverse.

There is a comfortable story that investors tell themselves about index funds. The story says that buying the whole market is humble, diversified, and efficient. You are not betting on any single company. You are simply renting the wisdom of the crowd at the lowest possible cost. For most of the history of indexing that story was close enough to true. It is no longer.

What has changed is not the philosophy but the plumbing. Passively managed funds now make up over fifty-five percent of US fund net assets, having crossed active in total assets back in 2023 and continued to pull away since. [1]

When a majority of the marginal dollar is mechanical, price-insensitive, and rules-bound, the character of the market itself changes. The index stops being a passive mirror of the economy and starts being an active force that moves the very prices it claims only to observe. That is the observation this piece is about, and it is a market-structure observation, not a valuation forecast.

The concentration is not an accident. It is the design working as intended.

Start with the fact that everyone now cites and few people sit with. By the end of 2025 the ten largest companies in the S&P 500 accounted for nearly forty-one percent of the index by weight, more than doubling in a single decade. That figure has since cooled, but only modestly. State Street's own SPY holdings, the cleanest real-time read on the actual index, put the top ten at 37.25 percent of weight as of July 9, 2026, with the full Magnificent Seven, including both Alphabet share classes, at 32.6 percent. A separate State Street snapshot one week earlier showed the top ten at 36.4 percent and the top twenty-five at just over half the index, a level strategists have not seen in roughly two decades. [2]

Not every source agrees on the exact number, and that disagreement is itself informative. S&P Dow Jones Indices data cited in mid-July put the top ten closer to forty percent of total index value, the most concentrated reading since the mid-1960s, with Nvidia, Apple, and Alphabet each now carrying market capitalizations above four trillion dollars. The gap between the thirty-seven and forty percent readings comes down to methodology, index weight versus raw market value, but the conclusion is identical either way: concentration eased slightly off its year-end peak without coming close to normalizing. [3]

Goldman Sachs frames it against a longer arc: the top ten are running around thirty-six to thirty-seven percent of market cap against a long-run average near twenty percent, and the dot-com peak in 2000 reached only about twenty-five. On one of their metrics, concentration is the highest since 1932. [4] [5]

The point is not that concentration is high. Everyone knows it is high. The point is why it is high, and the mechanical answer is uncomfortable. A cap-weighted index buys stocks in proportion to their size. When a dollar enters an S&P 500 fund, roughly thirty-seven cents of it is deployed into the ten largest names regardless of their valuation, their earnings quality, or their forward prospects. The buying is not a judgment. It is an arithmetic identity. Larger weights attract more of each incoming dollar, which lifts those weights further, which pulls in the next dollar on the same terms. The concentration eased a few points this year not because the mechanism broke, but because a handful of the largest names, Microsoft chief among them, actually underperformed even as the passive bid kept arriving. The design is still compounding. It is just compounding on a slightly reshuffled set of winners.