What are Capitalization-Weighted Index Funds?

What Are Capitalization-Weighted Index Funds?

By Catherine Brock – Updated Jun 14, 2025 at 10:59 PM EST

Key Points

Cap-weighted funds focus on large companies, impacting fund performance and risk.
These funds often feature lower expense ratios due to minimal trading requirements.
Consider your investment strategy when choosing between cap-weighted or equal-weighted funds.

Capitalization-weighted index funds are common, but do they fit your investment strategy? This guide can help answer that question. Let's explore the concept of weighting by market capitalization and how it affects the risk and performance of a fund.

A person using a calculator with financial charts on the desk. — Image source: Getty Images.

Loading image...

Understanding capitalization-weighted index funds

Capitalization-weighted index funds hold larger positions in big companies and lesser positions in smaller companies. In this context, a company is big or small based on its market capitalization. Market capitalization is the aggregate dollar value of the company's outstanding shares.

Other terms for this weighting strategy include cap-weighted or market cap-weighted.

Loading paragraph...

Weighting refers to the percentage of exposure to each stock. In a cap-weighted portfolio, the size of each position is determined by the company's market value relative to the total value of all stocks in the group. To demonstrate, let's create a fictitious index fund consisting of three positions:

Company A has a $1 million market capitalization.
Company B has a $550,000 market capitalization.
Company C has a $100,000 market capitalization.

The total market capitalization of the three companies is $1.65 million. Cap-weighting their stocks would create these exposures:

Stock A: 60.6%, or $1 million divided by $1.65 million.
Stock B: 33.3%, or $550,000 divided by $1.65 million.
Stock C: 6.1%, or $100,000 divided by $1.65 million.

Company A, the largest company in the group, has the highest weighting and, therefore, the most influence over the fund.

Many financial market indexes are capitalization-weighted, including the S&P 500, Nasdaq Composite, and the Wilshire 5000. Index funds that track these benchmarks directly are also weighted by market capitalization.

Loading paragraph...

Implications of market-cap weighting

The cap-weighted investing strategy has several implications:

Large companies have greater influence over the fund's performance than small companies. This can be an advantage or disadvantage, depending on your outlook.
Positions are not trimmed back as they grow and account for higher percentages of the fund. Depending on the portfolio composition, the fund may have to purchase more shares of stocks that are on the rise. This goes against the concept of rebalancing, which is intended to reduce overexposure to appreciating positions.
Heavier weighting of large, stable companies can contribute to lower portfolio volatility.
Cap-weighting increases exposure to fast-growing companies, which are most at risk of being overvalued. A bubble can result, which is great for returns -- until the bubble pops.
Cap-weighted index funds often have low expense ratios because they don't require heavy trading.

Three popular cap-weighted funds

The table below includes three popular cap-weighted funds along with their net assets, number of holdings, and 10-year returns. Also included is each fund's weighting of the three largest companies in the U.S. stock market: Microsoft (MSFT +3.04%), Apple (AAPL +0.68%), and Nvidia (NVDA -4.39%). These are the three largest positions in all three funds.

Loading paragraph...

Table data source: Vanguard.com, SSGA.com, ishares.com.
Fund metrics and data	SPDR S&P 500 ETF Trust (NYSEMKT:SPY)	Vanguard Growth ETF (NYSEMKT:VUG)	iShares Russell 1000 ETF (NYSEMKT:IWB)
Net assets	$544 billion	$220 billion	$36 billion
Benchmark index	S&P 500	CSRP U.S. Large Cap Growth Index	Russell 1000
Number of holdings	503	200	1,005
10-year average annual return	12.56%	14.89%	12.53%
Microsoft weighting	7.18%	12.53%	6.64%
Apple weighting	6.78%	10.81%	6.28%
Nvidia weighting	6.78%	8.86%	6.02%

Loading table...

The exposure percentages show there is a risk of overconcentration, especially if you are invested in more than one cap-weighted large-cap fund. Even so, the double-digit returns of these funds are compelling.

Performance: Cap-weighting versus equal-weighting

The effect of a fund's weighting strategy becomes more evident when you compare standard S&P 500 funds to equal-weighted S&P 500 funds. Equal-weighted funds ignore company size and hold similar percentages of all positions.

The table below shows returns of the S&P 500 and S&P 500 Equal Weight indexes.

Loading paragraph...

Table data source: Spglobal.com.
Timeframe	S&P 500 (Cap-Weighted)	S&P 500 Equal Weight Index
1-year return	26.27%	13.81%
3-year return	10.26%	4.58%
5-year return	15.33%	11.34%
10-year return	12.94%	10.22%

Loading table...

As you can see, weighting by market capitalization in the S&P 500 has been the superior strategy for the past decade. In the last three years specifically, the cap-weighted index more than doubled the returns of its equal-weighted counterpart.

Those outsized returns come primarily from extreme growth in a small group of very large technology companies. These stocks and their approximate average annual growth since June of 2021 are:

Microsoft: 25%
Apple: 24%
Nvidia: 232%
Alphabet (GOOG -1.03%): 15%
Meta (META -0.66%): 17%

Loading paragraph...

Related investing topics

Index Funds vs. Mutual Funds: Which Should You Choose?

Index funds and mutual funds both pool investors' money to buy many different securities. Learn how these investments work.

ETF vs. Index Fund: What's the Difference and Which Should You Choose?

Your investment style can dictate which kind of fund is best for your portfolio.

Loading hub_pages...

As long as these largest companies keep delivering the biggest gains, cap-weighting will outperform. If that trend changes and these heavyweights slow down, their sluggish performance could mask gains from the portfolio's smaller players.

So, is cap-weighting right for you? If you prefer to let a rising stock run, the answer may be yes. If you'd rather exit your winners and take profits before things go south, an equal weighting strategy could be the better fit.

Loading paragraph...

About the Author

Catherine grew up in Southern California wearing a lot of black and trying to perfect the art of sarcasm. Prior to joining The Fool as a contract writer, Catherine was climbing the corporate ladder in marketing roles and dabbling in too many side hustles. When she's not writing, she can be found riding a horse in the country or shopping online for clothes.

XMFCatherineJB

@catherinejbrock

Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool’s board of directors. Randi Zuckerberg, a former director of market development and spokeswoman for Facebook and sister to Meta Platforms CEO Mark Zuckerberg, is a member of The Motley Fool's board of directors. Catherine Brock has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Alphabet, Apple, Meta Platforms, Microsoft, Nvidia, and Vanguard Index Funds - Vanguard Growth ETF. The Motley Fool recommends the following options: long January 2026 $395 calls on Microsoft and short January 2026 $405 calls on Microsoft. The Motley Fool has a disclosure policy.