Narrow Market Breadth as Risk: Which Indices and ETFs Depend Less on Mega-Caps

Stock markets are increasingly dominated by a few very large companies. In the classic S&P 500 or MSCI World, mega-caps like Apple, Microsoft, Alphabet and Amazon determine a large portion of returns – and risk. Since 2023, this concentration has intensified further, as significant returns came from precisely these few stocks, while many traditional sectors and mid-sized companies lagged behind. Equal-weight indices take a different approach: they distribute capital equally across all holdings, offering a broader market base.

How Equal-Weight Indices Work

In an equal-weight index, each company receives the same weighting regardless of its market size. In a 500-title index like the S&P 500 Equal Weight, the weight per share is approximately 0.2 percent (Finanzen.net, May 2026). This contrasts with cap-weighted indices, where large companies weigh more heavily according to their market capitalization. In the classic S&P 500, the ten largest positions often account for over 30 percent of index weight.

To maintain equal distribution, equal-weight indices are regularly – typically quarterly – reset to their original weighting (Finanzen.net, May 2026; ETF-Rechner-Sparplan, July 2026). Between rebalancing dates, weights diverge again as prices move differently. Strong performers automatically receive higher weighting, weak holdings decline in proportion. At the next rebalancing, winning stocks are sold and losing stocks repurchased – a disciplined but transaction-intensive process.

Broader Diversification, Higher Costs

Equal-weight ETFs reduce concentration risk through more even distribution across sectors and companies (ExtraETF, July 2026). Because mega-caps are weighted smaller, the relative shares of mid-caps and smaller large-caps increase. These holdings are often valued more cheaply, giving the portfolio a value tilt (Finanzen.net, May 2026). Cap-weight, by contrast, emphasizes momentum and growth more strongly when a few large growth stocks dominate.

However, there is no free diversification. The regular resetting of weights requires more transactions overall, which typically leaves the efficiency advantage on the side of classic cap-weight ETFs (Finanzen.net, May 2026). Equal-weight ETFs often result in higher ongoing costs and greater tracking difference – meaning deviation between index returns and actual fund returns – than cap-weight products.

When Equal Weight Falls Behind

In phases when mega-caps drive the market, cap-weight often outperforms equal-weight significantly. Historically, investors with broadly diversified, market-weight-indexed ETFs receive average returns of around 8 percent per year (ETF.capital). The years since 2023 have been precisely such a phase: a few very large tech stocks provided the bulk of index gains, while market breadth lagged.

Counterexample from the tech sector: The Amundi US Tech 100 Equal Weight ETF DR Income (ISIN: IE000Y9MG996) achieved 1-year performance of +21.18 percent and 3-year performance of +72.63 percent according to Finanzen.net in May 2026. This shows that equal weight can perform well in specific sectors and market phases – but this is no guarantee for sustained better returns.

Risk Profile: Different, Not Automatically Safer

Equal weight does not automatically mean greater safety, but rather a different distribution. Investors reduce one specific risk – dominance by very large individual stocks – but simultaneously increase other risks: more turnover, greater deviation from the standard index, higher weight in less dominant companies and potentially higher costs (ETF-Rechner-Sparplan, July 2026).

Those wanting to hedge concentration risk must therefore be willing to accept the drawbacks. In market phases with high concentration – such as since 2023 – equal weight offers stability through a broader market base and balances the concentrated S&P 500 (FT Deutschland, February 2026). Whether this tradeoff is worthwhile depends on individual risk tolerance and expectations about future market development.

Alternatives for Maximum Diversification

Equal weight is not the only way to increase market breadth. For maximum diversification including small-caps, the MSCI ACWI IMI is recommended. The SPDR MSCI ACWI IMI (IE00B3YLTY66) covers 99 percent of the investable market and, according to Dividendenknecht in September 2026, delivers excellent cost efficiency.

Most well-known ETFs on the S&P 500 or MSCI World weight by market capitalization (Finanzen.at, March 2026). This standard approach remains the most efficient way for many investors to track the market. Those wanting to deliberately reduce concentration risk can use equal-weight products as a satellite position or switch to more broadly diversified indices with small-caps.

Assessment for 2026: Renewed Interest in Market Breadth

Equal weight could come back into focus in 2026. Possible arguments include persistent market concentration, high valuations in mega-caps and potential mean reversion, which support broader diversification (TheMarket.ch, February 2026). Whether these expectations materialize remains to be seen – history shows that market phases with strong concentration can persist for years.

Equal-weight ETFs offer a conceptually attractive alternative to reduce mega-cap overweighting and bring more breadth to a portfolio. Professionals also use the approach to increase exposure to factors such as size and valuation (Finanzen.net, May 2026). However, the concept regularly incurs higher transaction costs through rebalancing, often higher ongoing costs and, in phases when large tech stocks drive the market, worse returns than cap-weight alternatives. They thus represent more of a consciously chosen alternative factor than a universally better diversification approach.