How a Stock Gets Into the S&P 500 and the Nasdaq-100

A place in the S&P 500 or the Nasdaq-100 matters because of the money that follows these indexes. S&P Dow Jones Indices counted about US$16 trillion in assets indexed to the S&P 500 at the end of 2025, a figure that includes exchange-traded derivatives. Nasdaq says the Nasdaq-100 is tracked by more than 200 investment products with over US$800 billion in assets. A fund built to follow an index holds what the index holds, so a change in membership is also a change in what those funds own.

The two indexes choose their members in very different ways. The S&P 500 is run by a committee that uses judgment within written criteria. The Nasdaq-100 follows a rulebook, and its list changes on a fixed calendar. Our guide to the Dow, the S&P 500 and the Nasdaq covers what each index measures; this one covers how companies get in and out.

The two side by side

	S&P 500	Nasdaq-100
Who decides	An Index Committee at S&P Dow Jones Indices	Written rules, applied by Nasdaq
Schedule	As needed; no scheduled reconstitution	Annual reconstitution in December, quarterly reviews in March, June and September
Notice	At least three business days, announced at 5:15 p.m. New York time	After the close, six trading days before a reconstitution takes effect
Who can be in	US-domiciled companies on eligible US exchanges	Non-financial companies listed primarily on Nasdaq
ADRs	Not eligible	Eligible

How does the S&P 500 choose?

A committee decides. The methodology says the Index Committee “meets monthly” and that “there is no scheduled reconstitution.” Changes are made “on an as-needed basis” and announced “with at least three business days advance notice,” at 5:15 p.m. Eastern time. The committee may give less notice at its discretion.

Candidates must first pass the rules. A company must be US-domiciled, be worth at least US$22.7 billion (the level set on July 1, 2025, and reviewed every quarter), have at least 10% of its shares available to public investors, trade often enough, and have positive GAAP earnings in the latest quarter and over the latest four quarters added together. An initial public offering must normally trade on an eligible exchange for at least 12 months first; the methodology says there is “no IPO fast track” for the S&P 500. ADRs are not eligible.

Passing the rules does not guarantee a place. The committee picks from eligible companies when there is a reason to make a change. Two kinds of change are common:

• Quarterly rebalance additions. In 2026 the committee announced its main batches of additions about two weeks ahead of each quarterly rebalance: on March 6 (effective March 23), June 5 (effective June 22) and September 4 (effective September 21). Each took effect before the open on the Monday after the third Friday of the month.
• Replacements when a member leaves. When a member is bought or merged away, another company takes its seat. SanDisk joined the S&P 500 effective November 28, 2025, replacing The Interpublic Group, which Omnicom Group was acquiring. SanDisk moved up from the S&P SmallCap 600.

Staying in is easier than getting in. The methodology says “the eligibility criteria are for addition to an index, not for continued membership.” A member that falls below the size threshold is not removed automatically. The committee may remove a company that “substantially violates” the criteria, and a company that is removed must wait at least a year before it can come back.

Chip company changes in 2026 (S&P Dow Jones Indices releases):

Effective	Change
March 23	Micron, Lam Research and Applied Materials joined the S&P 100
June 22	Marvell Technology joined the S&P 500
September 21	SanDisk joined the S&P 100

The S&P 100 is a smaller index of large S&P 500 members; a move into it does not change a company’s place in the S&P 500.

How does the Nasdaq-100 choose?

Rules decide. The Nasdaq-100 takes the largest non-financial companies whose shares are listed primarily on Nasdaq (not on the Nasdaq Capital Market tier), ranked by market value. Nasdaq rewrote the rules after a public consultation, and the new methodology took effect on May 1, 2026.

The basic requirements under the 2026 methodology:

• an average of at least US$5 million a day in shares traded over three months;
• no minimum free float, but a company with few freely traded shares has its weight capped at three times its free-floating shares;
• not in bankruptcy;
• for the December reconstitution, listed on Nasdaq no later than the last trading day of August. For a newly listed ADR, Nasdaq’s FAQ says “a prior foreign listing trading history does not count toward this seasoning requirement.”

Each class of a company’s shares can be eligible on its own. For an ADR whose company has its main listing abroad, only the value of the receipts listed on Nasdaq counts.

The annual reconstitution follows a fixed calendar. Companies are ranked on the last trading day of November. The changes are announced after the close six trading days before they take effect, at the open on the first trading day after the third Friday in December. The selection runs in order:

1. The 75 largest eligible companies are selected.
2. Current members ranked within the top 100 stay.
3. Current members ranked 101st to 125th also stay, if they were in the top 100 at the previous reconstitution or were added since.
4. The largest remaining non-members fill the open places.

For 2026, that calendar puts the ranking on Monday, November 30, the announcement after the close on Friday, December 11, and the changes at the open on Monday, December 21. Those dates come from the rules; Nasdaq had not published its own notice as of October 23.

The quarterly reviews are new in 2026. In March, June and September, a member ranked outside the top 125 is removed and replaced by the largest eligible non-member, and any eligible company ranked within the top 40 that is not yet a member is added. This replaced the earlier rule that removed a member whose weight stayed below 0.10% at two month-ends.

Vacancies in between are filled by “the company with the largest Full Market Capitalization that meets all eligibility criteria” and is not already a member. A large new listing can also take a “Fast Entry” route: it is ranked on its seventh trading day, announced after its tenth and added after 15.

Chip, storage and chip-equipment company changes (Nasdaq announcements):

Effective	Change
December 22, 2025	Monolithic Power Systems, Seagate and Western Digital joined; GlobalFoundries and ON Semiconductor left
April 20, 2026	SanDisk replaced Atlassian
June 22, 2026	Astera Labs and Teradyne joined in the first quarterly review under the new rules

Where do the Asian chipmakers stand?

Company	What trades in the US	S&P 500	Nasdaq-100
TSMC	ADSs on the NYSE (TSM)	Not eligible: an ADR, and not US-domiciled	Not eligible: not listed on Nasdaq
SK hynix	ADSs on Nasdaq (SKHY) since July 10, 2026	Not eligible: an ADR, and not US-domiciled	Eligible to be ranked, at the value of the ADSs only
Samsung Electronics	No US listing	Not eligible	Not eligible
Kioxia	Over-the-counter receipt (KXIAY)	Not eligible	Not eligible

SK hynix is the case to watch in December. Its ADSs, each worth one-tenth of a common share according to its prospectus, were listed before the end of August, which meets the listing cutoff for the 2026 reconstitution. Meeting the rules is not the same as getting in: the ADSs would still have to rank high enough, and only the value of the ADSs counts, not the whole company. Nasdaq’s ranking on November 30 decides it.

TSMC does appear in one widely followed US index: Nasdaq’s semiconductor index, the SOX, which accepts ADRs listed on any eligible US exchange. Our SOX explainer covers its rules, and Asia Chip Stocks From a US Account explains what each US-traded ticker represents.