Total-Market, S&P 500 or International: What Each Index Holds

What a US total-market index, the S&P 500 and two international indexes actually hold, according to their providers' own rules, and how to check which index a fund follows.

Published by Greg M., Editor in Chief · Updated November 9, 2026

An index fund doesn’t choose its own holdings. It follows an index, and the index provider’s rulebook decides what’s in it. The SEC’s Investor.gov describes an index fund as following a passive strategy designed to achieve approximately the same return as a particular index before fees, by investing in the securities in that index or, in some cases, a representative sample of them (Investor.gov, “Index Fund”, checked November 9, 2026).

So “what does this fund own?” is really “what does this index include?” This guide describes four widely used broad stock indexes from four providers, using each provider’s own methodology or factsheet, dated. They’re named only to show how index rules work, not as a recommendation of any index or fund, and the guide doesn’t compare which one is better to own. Index rules change, and the dates below show which version was read.

Three questions that describe any index

Before the details, it helps to know what to look for in any index’s rules:

• Which companies are eligible? Usually defined by country, the exchanges where shares are listed, and security type (for example, common stock but not preferred stock).
• How much of the eligible market does it cover? Some indexes hold only large companies; others reach into mid, small and even micro caps.
• How are holdings weighted? All four indexes below weight by market value adjusted for “free float,” meaning shares available to the public. Bigger companies therefore carry bigger weights.

The US total-market index: nearly everything listed in the US

The index many people know as the CRSP US Total Market Index now has a new name. Morningstar’s July 2026 methodology guide says Morningstar acquired CRSP in February 2026 and that the CRSP indexes were rebranded the Morningstar Market Indexes in July 2026 (Morningstar Market Indexes Methodology Guide, effective July 17, 2026, checked November 9, 2026). Documents written before then use the CRSP name.

According to that guide, the Morningstar US Total Market Index is designed to represent the entire US investable equity market:

• What’s eligible: common stocks and real estate investment trusts (REITs) of US companies listed on NYSE, NYSE American, NYSE Arca, Nasdaq and Cboe BZX. The guide adds that the Texas Stock Exchange becomes eligible after September 30, 2026.
• What’s excluded: among others, American depositary receipts, preferred stock, closed-end funds, ETFs and ETNs, limited partnerships, royalty trusts and SPACs.
• US company test: generally based on where a company is incorporated and headquartered, with further tests for companies that meet only one of those.
• Weighting and changes: float-adjusted market capitalization weighting, a quarterly reconstitution schedule, and quarterly changes applied over a five-day transition window.

The same guide splits the market into size segments using cumulative market-cap breakpoints set at 70%, 85% and 98% of the eligible universe. Companies are ranked from largest to smallest by cumulative share of the market’s value. Roughly, the first 70% are mega caps, 70% to 85% are mid caps (mega and mid together form the large-cap index), 85% to 98% are small caps, and micro caps lie beyond 98%, with bands around each breakpoint to limit turnover. The total-market index includes all of these segments.

The S&P 500: large US companies that pass size and earnings tests

S&P Dow Jones Indices’ own website could not be accessed when this guide was researched, so the S&P 500 rules below come from a fund prospectus filed with the SEC that summarizes them (SPDR Series Trust prospectus filing, SEC EDGAR, filed August 27, 2026, dated September 1, 2026, checked November 9, 2026). The filing is cited only as a source document for the index rules, not as a recommendation of that fund or of the index. S&P’s methodology document remains the authoritative version.

According to that filing, the S&P 500 measures the large-capitalization segment of the US equity market. To be added, a company’s common stock must be listed on one of the eligible US exchanges and, at the time of that filing, generally:

• have an unadjusted market capitalization of at least $22.7 billion and a float-adjusted market capitalization of at least $11.35 billion at the time of inclusion;
• have a public float of at least 10%;
• have positive aggregate earnings over the four most recent quarters and for the most recent quarter;
• trade at least 250,000 shares in each of the six months before the evaluation date.

The filing describes the index as float-adjusted market-cap weighted and rebalanced quarterly in March, June, September and December, with constituents added and removed as needed. It also notes that, as of June 30, 2026, the index comprised 503 stocks, so the “500” in the name is a label rather than an exact count.

The size threshold is a moving figure that S&P updates, which is why a dated source matters. The profitability test is a feature of the S&P 500’s own rules, alongside its size and liquidity requirements.

How the two US indexes relate

Both indexes draw on common stocks listed on US exchanges, and both weight by float-adjusted market value, so the largest US companies carry large weights in each. The clearest difference is at the smaller end. The total-market index reaches down through mid, small and micro caps, while the S&P 500’s size threshold limits it to large companies, and its earnings and liquidity tests add further conditions.

What that means for a holder is a question of what’s included, not of which performs better. Neither the providers’ rules nor past results say which will do better in the future.

International indexes: everything outside the US

International indexes for US investors usually exclude the US by design. Two examples from different providers show how they can differ.

MSCI ACWI ex USA Index. As of October 30, 2026, MSCI’s factsheet says the index captures large and mid cap representation across 22 of 23 developed-market countries (excluding the US) and 24 emerging-market countries, with 1,899 constituents covering approximately 85% of the global equity opportunity set outside the US (MSCI ACWI ex USA Index factsheet, data as of October 30, 2026, checked November 9, 2026). On that date its largest country weights were Japan (14.35%), Taiwan (9.13%), the United Kingdom (8.83%), Canada (8.65%) and China (6.33%), with all other countries making up 52.71%. On the same date, its 10 largest holdings together made up 15.72% of the index. The factsheet lists every country and points to MSCI’s index methodology for the full rules.

FTSE Global All Cap ex US Index. FTSE Russell’s ground rules for its Global Equity Index Series say the series covers securities in 49 countries, divided into developed, advanced emerging and secondary emerging segments, and that the Global All Cap series includes large, mid and small cap stocks (FTSE Global Equity Index Series Ground Rules v14.4, September 2026, checked November 9, 2026). The rules list a FTSE Global All-Cap ex US Index among the indexes calculated, define each regional index universe as the top 98% by weight of that region’s ranked companies, and adjust constituents for free float and foreign ownership limits. Reviews are held in March and September, with quarterly reviews in June and December.

Comparing the two descriptions shows the kinds of differences to look for: MSCI’s index covers large and mid caps, while FTSE’s all-cap index also includes small caps. Each provider also publishes its own country classification, so the developed and emerging labels, and which countries are included at all, come from that provider’s list. Checking the list is the way to see what a particular index holds.

How to check what a fund actually follows

A fund’s name doesn’t always tell you its index. What to check in its documents:

• The exact index name and provider, usually in the summary prospectus under the fund’s principal investment strategy. Reading a prospectus fee table shows where to find it.
• Whether the fund holds every security or a sample. Investor.gov notes that some index funds invest in a representative sample of the index or use derivatives.
• The number of holdings and the date of that count, which shows roughly how broad the index is.
• The index’s own methodology or factsheet, dated, for the rules behind the holdings.
• The fund’s costs, which come out of what the index earns. See what an expense ratio costs and the fee-drag calculator.

How these indexes might fit into a mix of investments is a separate question covered in diversification and asset classes and asset allocation by time horizon.

Common questions

Is a total-market index fund the same as an S&P 500 fund? No. Both hold large US companies, but a total-market index also includes mid, small and micro caps, and the S&P 500 adds an earnings requirement for new members.

Does the S&P 500 hold exactly 500 stocks? Not always. The SEC filing cited above reports 503 stocks as of June 30, 2026.

Do international indexes include the US? The “ex USA” and “ex US” versions described here exclude it by design. For any other global index, the provider’s country list shows whether the US is in it.

Why can two international funds hold different things? Each provider sets its own country classification and size coverage. As of the October 30, 2026 factsheet, the MSCI index described here holds large and mid caps; the FTSE all-cap index also includes small caps.

Can I invest in an index directly? No. An index is a list and a set of rules. Funds that track an index are the usual way to get exposure, and they charge fees that the index itself doesn’t.

Sources checked November 9, 2026: Morningstar Market Indexes Methodology Guide (July 2026, formerly CRSP); SPDR Series Trust prospectus filing with S&P 500 index description, SEC EDGAR (dated September 1, 2026; source document for the index rules only, not a recommendation); MSCI ACWI ex USA Index factsheet (October 30, 2026); FTSE Global Equity Index Series Ground Rules v14.4 (September 2026); SEC Investor.gov, Index Fund.