The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →You can own several funds and still be heavily exposed to the same handful of mega-cap companies. To diversify deliberately, look through the holdings across your entire portfolio, identify the concentration you want to reduce, then compare broader or differently weighted investments by their actual exposures—not by fund count or name.
Why a 500-stock fund can still be concentrated
Many broad index funds weight companies by market capitalization, so the largest companies take the largest shares. The S&P 500 is float-adjusted market-cap weighted and covers approximately 80% of available U.S. market capitalization, according to S&P Dow Jones Indices. As of August 31, 2026, its top 10 constituents made up 37.8% of the index and its largest constituent made up 8.1%. The index had 503 constituents at that date; a large company count does not mean equal-sized positions.
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That does not make the index inherently unsuitable. It means the label “500 stocks” alone does not tell you how much of your money is tied to the biggest names. The same issue can arise when you hold multiple funds: they may own many of the same companies. The SEC recommends checking funds’ top holdings for overlap; see Asset Allocation and Diversification.
Measure concentration across your whole portfolio
Start with a look-through inventory rather than a list of account or fund names. Include workplace retirement plans, IRAs, taxable accounts, and concentrated employer shares. Where fund holdings are available, combine exposures to the same companies across funds and accounts. Then examine sector, country, and asset-class weights as well as individual company weights.
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This makes the problem specific. A portfolio may be concentrated in U.S. mega-caps, one sector, one country, equities overall, or employer stock. Those are different exposures, and adding more tickers may not address any of them. The SEC notes that allocation choices should reflect a person’s risk tolerance and timeframe; its Beginners’ Guide to Asset Allocation, Diversification, and Rebalancing also describes diversification within and between asset categories.
Choose what kind of diversification you need
Broaden company and sector exposure
One option is to use an investment with a different weighting method or broader company exposure. A reweighted index can reduce the influence of the largest market-cap names, but it remains an equity investment and can behave differently from a market-cap-weighted benchmark. It is not automatically safer or more profitable.
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For example, the S&P 500 Diversified Sector Weight Index reweights companies within the S&P 500 with the stated goal of reducing concentration risk and sector imbalances. Its methodology uses equal weights at multiple business-classification levels and revenue-proportional weights within each business activity. S&P DJI lists the Xtrackers S&P 500 Divers Sect Weight ETF (SPXD) as linked to the index. This describes a construction approach, not a recommendation or a guarantee of outcomes.
Broaden beyond one country
International stocks can extend exposure beyond the United States, but a global market-cap-weighted index is not evenly divided among countries or companies. In the MSCI ACWI comparator data published in the MSCI ACWI Momentum Tilt Index (USD) factsheet dated September 30, 2026, ACWI had 2,414 constituents, a 5.11% largest constituent weight, and a 23.92% top-ten weight. The United States accounted for 58.65% and information technology for 40.84%. These are dated index characteristics, not a timeless allocation target or a description of every fund that references the index.
Consider the mix of asset categories
Diversification can also mean allocating among stocks, bonds, and cash, rather than holding only equities. These assets have different risks and may affect expected volatility, returns, liquidity, and taxes. No single mix fits every investor; the relevant choices depend on the purpose of the money, time horizon, and ability to tolerate losses. Diversification can lower overall portfolio risk, as the SEC puts it, but it does not prevent losses.
Compare options by what they actually hold
Before adding or replacing an investment, compare its role with the exposures already in your portfolio. Fund names and the number of holdings can obscure meaningful differences in concentration and risk.
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- Company concentration: compare the largest holding and top-ten weights where published.
- Weighting method: determine whether holdings are market-cap weighted, equally weighted, or reweighted another way.
- Sector and country mix: check whether the investment reduces the particular exposure you identified.
- Breadth: see whether it adds company sizes, regions, or asset categories that are missing.
- Overlap: check whether its major holdings already appear in other funds or accounts.
- Costs and mechanics: review current expenses, turnover, trading costs, tracking difference, tax consequences, and benchmark role in the fund documents and under the rules that apply in your jurisdiction.
Index factsheets show index construction and exposure, not necessarily the exact holdings, expenses, tax treatment, or performance of a particular fund. Check the current fund documents before acting.
Set a rebalancing rule and review it infrequently
Once you have a target allocation, rebalancing is the maintenance decision about how to bring the portfolio back toward it when weights drift. The SEC describes two common approaches: review on a calendar schedule or rebalance when an asset moves beyond a preset threshold. It gives six- or twelve-month reviews as examples and says rebalancing tends to work best relatively infrequently. These are general approaches, not personalized instructions; consider transaction costs and tax consequences before making changes.
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