The SPDR S&P 500 ETF Trust holds 504 stocks and still carries 37.83 percent of its weight in information technology as of 15 September 2026. Counting tickers measures none of that. What sets the number is the share of the account tied to one factor, and five names can put that share at 100 percent.
Concentration is a share, not a count
FINRA's investor page defines concentration risk as the risk of amplified losses from having a large portion of your holdings in a particular investment, asset class or market segment relative to the whole portfolio. Every term in that sentence is a proportion. The same FINRA page lists how the proportion grows without anyone deciding to grow it: a holding that outruns the rest takes a larger slice of the account, employer stock piles up inside a retirement plan, and positions in one industry, one region or one security type move together.
So five tickers can be five slices of the same factor. The SEC's investor education site makes the matching point about funds: a fund will not necessarily diversify a portfolio, and the page tells an investor holding several to check the top holdings of each fund to see whether they are actually different.
Worked example: $10,000 across five names
This example uses a published sector weight and an example price move for the sector itself. Take $10,000 split into five equal $2,000 positions, all of them information technology companies. The technology share of that account is 100 percent. A 20 percent fall in the sector takes $2,000, which is 20 percent of the account.
Hold the same $10,000 in the SPDR S&P 500 ETF Trust and the technology share is 37.83 percent, or $3,783. The same 20 percent sector fall takes 0.3783 times 20 percent, which is 7.57 percent of the account, or $756.60.
Split the money — $5,000 in the fund and $5,000 in one technology stock — and the share is 50 percent plus half of 37.83 percent, or 68.92 percent. A 20 percent sector fall then costs 13.78 percent, or $1,378.30. Three different ticker counts, one factor, three different losses.
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| Portfolio of $10,000 | Share in information technology | Loss if that sector falls 20 percent |
|---|---|---|
| Five equal technology positions | 100 percent | $2,000 |
| One S&P 500 fund | 37.83 percent | $756.60 |
| Half the fund, half one technology stock | 68.92 percent | $1,378.30 |
What the fund page actually reports
Every weight above comes from the fund's own page, dated 15 September 2026 and listing 504 fund holdings against 503 in the index. The other ten sectors run financials 12.26 percent, communication services 10.03 percent, health care 9.24 percent, consumer discretionary 8.82 percent, industrials 8.12 percent, consumer staples 4.53 percent, energy 3.65 percent, utilities 1.96 percent, materials 1.78 percent and real estate 1.78 percent. The eleven weights add to 100 percent. Add the bottom seven and the total is 30.64 percent, less than the 37.83 percent sitting in the single largest sector. A 504-stock fund is the diversified end of the range, and it still leans.
The gross expense ratio on that fund is 0.0945 percent a year, which is the cost of owning the whole list rather than picking from it. Reading a fund's stated objective and holdings before its price chart is the work covered in the guide on what an ETF objective tells you, and the difference between the measurement and the product is set out in the guide on an index versus a fund.
Rebalancing moves the share back
Drift is arithmetic, not neglect. The SEC's asset allocation page gives the case of a portfolio that starts at 60 percent stocks and reaches 80 percent on market gains alone, and notes that some advisers rebalance at fixed intervals of six or 12 months while others rebalance when a class moves past a pre-set percentage. Either rule acts on the share, which is the quantity that decides the loss.
The number to check before the names
The check is one division: position value over account value, then the same sum grouped by sector, by industry and by the factor a group of names responds to. Run it through the funds as well, because a fund's weights become the account's weights. How much of that share a portfolio can carry is a separate question, handled in the guide on risk tolerance and the ability to absorb a loss.
Source references
Primary sources used for this guide. Follow the links for the original scope, definitions and conditions.
- SPY: State Street SPDR S&P 500 ETF TrustAccessed 2026-09-17
- Concentrate on Concentration Risk | FINRA.orgAccessed 2026-09-17
- Asset Allocation and Diversification | Investor.govAccessed 2026-09-17