Indexy a trhy
Index Weighting: Market Cap vs. Equal Weight
Key takeaways
- Market-cap-weighted indexes give the largest companies the greatest representation.
- Equal weighting spreads exposure evenly — every company receives the same share.
- Cap weighting leads to stronger concentration in top holdings.
- Equal-weight ETFs rebalance portfolios back to even weights, automatically "buying cheap".
- The choice of weighting method affects sector exposure, volatility, and management costs.
The weighting method determines how much of your ETF ends up in each company — and thus fundamentally shapes the resulting return and risk of the portfolio.
Market-capitalization weighting
The vast majority of global indexes — the S&P 500, MSCI World, or the Nasdaq-100 — use market-cap weighting. A company with a higher stock-market value receives a larger share of the index. The result is an automatic preference for "winners": as a company grows, its weight in the index rises proportionally.
The advantage is low portfolio turnover and generally lower costs. The disadvantage is concentration: the five largest companies in the S&P 500 can account for more than 25% of the entire index. We discuss the concentration issue in more detail in a dedicated article.
Equal weighting
An alternative is equal weighting: every company receives the same share of the index — for instance, 0.2% across 500 stocks. The index is rebalanced regularly to maintain this balance. This results in automatic selling of pricier holdings and buying of cheaper ones — a mechanism similar in principle to cost averaging.
Equal-weight indexes have historically outperformed cap-weighted variants by a small margin, but at the cost of higher volatility and higher transaction costs at rebalancing.
Other weighting methods
Additional approaches exist:
- Fundamental weighting (dividends, earnings, book value) — the basis of so-called smart-beta investing.
- Volatility weighting — lower weight goes to more volatile stocks.
- Price weighting — the Dow Jones Industrial Average works this way; companies with a higher share price have more influence.
What this means for your portfolio
For a long-term passive investor, cap weighting is generally sufficient — low costs and natural exposure to winners are strong arguments. Equal weighting makes sense as a complement for diversification or for investors convinced of a value approach. The basics of ETF selection are covered in the ETF Navigator.
FAQ
What is market-cap index weighting?
A company with a higher market value receives a larger share of the index. As the company grows, its weight grows. The result is natural exposure to large successful companies, but also higher concentration in top holdings.
How does an equal-weight index differ?
Every company receives the same share regardless of size. The index is regularly rebalanced back to equal weights — automatically buying cheaper holdings and selling more expensive ones. This comes at the cost of higher expenses and turnover.
Which weighting method is better for a long-term investor?
Cap weighting is the most common in passive investing due to low costs and simplicity. Equal weighting can reduce concentration, but has a higher TER. It depends on your strategy and tolerance for volatility.