The Russell Microcap Index is a benchmark tracking roughly 2,000 of the smallest publicly traded companies in the United States, maintained by FTSE Russell. It is built by taking the smallest 1,000 companies in the Russell 2000 and extending downward to the next 1,000 eligible securities, drawn from a universe of up to the 4,000 largest US stocks by total market capitalization. Membership is decided by ranking, not by a fixed dollar figure, so the boundary moves every time the index is rebuilt.
Joining matters because passive money follows the index. It does not matter because inclusion says anything about the quality of a business.
Source: FTSE Russell, "Russell US Indexes Construction and Methodology," July 2026.
How the index is constructed
FTSE Russell ranks eligible US companies by total market capitalization on a single rank day. The largest 1,000 form the Russell 1000. The next 2,000 form the Russell 2000. Together those two make the Russell 3000.
The Russell Microcap Index overlaps the bottom of that structure rather than sitting cleanly beneath it. It takes the smallest 1,000 members of the Russell 2000 and adds the next 1,000 eligible securities below them. Combining the Russell 3000 with the Russell Microcap produces the Russell 3000E, which covers up to the 4,000 largest US stocks and is the broadest of the family.
The practical consequence of ranking is that no company knows in advance where the line will fall. A business can grow and still drop out, if others grew faster. The breakpoint between the Russell 1000 and Russell 2000 rose 24% to $5.7 billion at the June 2026 reconstitution, which gives a sense of how far these boundaries can travel in a single year.
Sources: FTSE Russell, "Russell US Indexes Construction and Methodology," July 2026. Breakpoint figure per the FTSE Russell June 2026 semi-annual Russell US Indexes Reconstitution announcement, published via LSEG.
How a company gets in
Size ranking decides which index a company lands in. Eligibility decides whether it is ranked at all. The screens are mechanical and published.
| Criterion | Requirement |
|---|---|
| Exchange | CBOE, NYSE, NYSE American, Nasdaq, or ARCA. Bulletin board, pink sheet, and over-the-counter securities are not eligible. |
| Minimum share price | $1.00 closing price on the primary exchange on rank day. A 30-day average applies to existing members. |
| Minimum market capitalization | $30 million total market capitalization on rank day. |
| Free float | At least 5% of shares available to the public. |
| Voting rights | At least 5% of voting rights, aggregated across all equity securities, held by unrestricted shareholders. |
| Excluded structures | Royalty trusts, US limited liability companies, closed-end investment companies, blank check companies, SPACs, limited partnerships, ETFs, and mutual funds. |
| Excluded share types | Preferred and convertible preferred, redeemable shares, participating preferred, warrants, rights, depositary receipts, installment receipts, and trust receipts. |
Sources: FTSE Russell, "Russell US Indexes Construction and Methodology," July 2026, and FTSE Russell Insights, "How can my company get into the Russell indexes?"
Newly listed companies are picked up at the semi-annual reconstitutions and at quarterly reviews in March and September. In May 2026 FTSE Russell confirmed a Fast Entry rule following a February consultation, under which sufficiently large IPOs can be added after the close of the fifth trading day rather than waiting for a scheduled review. That threshold is keyed to the Russell Top 500 breakpoint, so it is a large-company mechanism and rarely touches this end of the market.
Source: FTSE Russell, "FTSE Russell introduces IPO Fast Entry enhancements for Russell US Indexes," May 2026, published via LSEG.
Reconstitution, and what changed in 2026
Reconstitution is the annual rebuild that recalculates every breakpoint and reassigns every constituent. For decades it happened once a year in June. From 2026 it happens twice, with a second rebalance added in December.
| Stage | June 2026 date | What happens |
|---|---|---|
| Rank day | April 30, 2026 | Market capitalizations are measured. Everything downstream is fixed by this date. |
| Preliminary lists | May 22, 2026 | Projected additions and deletions published to the market. |
| Updates | May 29, June 5, 12, 18 | Revisions to the preliminary lists. |
| Effective | After close, June 26, 2026 | New membership takes effect. Tracking funds trade to match. |
| Second rebalance | December 2026 | New for 2026. Addresses market capitalization changes primarily. |
Sources: FTSE Russell reconstitution schedule and the June 2026 semi-annual Russell US Indexes Reconstitution announcement, published via LSEG. December scope per FTSE Russell, "Russell US Indexes Construction and Methodology," July 2026.
The gap between rank day and effective date is nearly two months, and preliminary lists circulate for five weeks before the switch. Nothing about this event is a surprise to anyone paying attention, which matters for the section that follows.
Why inclusion moves a small stock more than a large one
Approximately $12.2 trillion in investor assets is benchmarked to or invested in products based on the Russell US Indexes. Funds tracking an index do not exercise judgment about membership. When the constituent list changes, they trade to match it. That concentration of forced trading is why reconstitution is consistently one of the highest-volume days of the year: $217.2 billion changed hands at the close of the June 2025 reconstitution.
The arithmetic of why this lands harder at the bottom of the market is straightforward. A fixed dollar amount of buying is a rounding error against a company with billions of dollars of stock in public hands. The same buying against a company with a $60 million float and a $1.00 minimum share price is a meaningful fraction of everything available. Index demand is set by the index weighting, not by what the stock can comfortably absorb.
The counterweight is that none of this is hidden. Preliminary lists are published weeks ahead and the effective date is known a year in advance, so the trade is anticipated by anyone who wants to anticipate it. We treat inclusion as a liquidity event with a known date, not as information about a business. Two things follow from that framing, and they pull in opposite directions: reconstitution can temporarily make a thin stock look liquid, and it can just as easily reverse when the flow stops.
Scale is not constant year to year. Third-party analysis from Acuitas Investments reported that the Russell Microcap Index added 252 new stocks in the June 2026 reconstitution, described as the largest cohort of new entrants in nearly half a decade and roughly a 50% increase on the prior year. That is a house estimate rather than an FTSE Russell figure, and worth treating as such.
Sources: benchmarked assets and June 2025 closing volume per the FTSE Russell June 2026 reconstitution announcement, published via LSEG. Entrant count per Acuitas Investments commentary published by WealthManagement.com, July 2026.
What the index is not
This is the part most explainers leave out. The Russell Microcap Index is not the microcap universe. It is the listed, screened, investable slice of it, and the screens remove a great deal.
| Russell Microcap Index | Our coverage universe | |
|---|---|---|
| Approximate size | Around 2,000 securities | Around 2,400 names |
| OTC securities | Excluded entirely | OTCQX included |
| Sub-$1.00 shares | Excluded | Eligible, subject to the volume floor |
| Below $30 million cap | Excluded | Eligible, subject to the volume floor |
| Upper boundary | A floating rank, not a dollar figure | $500 million, tested at publication |
| Rebuilt | Twice a year from 2026 | Screened weekly |
Sources: index criteria per FTSE Russell, "Russell US Indexes Construction and Methodology," July 2026. Coverage universe per the MicroCap Desk methodology page. The two counts are not directly comparable, since the universes overlap only partially.
The OTC exclusion is the widest of these gaps. A large share of what people mean by microcap trades over the counter and is therefore invisible to the index and to every fund tracking it. That is a reasonable design choice for a benchmark, since an index needs investability. It is also the reason nobody should use index membership as a proxy for the size of the opportunity set.
Common mistakes
- Treating inclusion as a quality signal. The screens test size, price, float, voting rights, and legal structure. None of them tests whether the business works, whether the filings are current, or whether the company can fund itself to next year.
- Treating a reconstitution move as a rerating. Flow-driven price movement around a known calendar event and a change in what a company is worth are different things. The first has an end date.
- Assuming the index covers the microcap market. It excludes the entire OTC market by rule.
- Reading a deletion as a verdict. A company can be removed for growing into a higher tier, for falling below $1.00, for a float that dropped under 5%, or because 2,000 other companies simply ranked higher.
- Forgetting the calendar changed. Anyone working from the assumption of a single June event will be surprised by December 2026.
What to check around reconstitution season
- Know the rank date, not just the effective date. Everything is decided on rank day. Price action after it does not change membership.
- Read the preliminary lists from the source. FTSE Russell publishes projected additions and deletions weeks ahead, and revises them. Secondary reporting often quotes the first version.
- Separate flow volume from normal volume. Compare volume in the reconstitution window against the trailing average. A single day of index-driven trading is not evidence of durable liquidity.
- Check the eligibility screens against the company. A share price near $1.00 or a float near 5% puts membership at risk regardless of size.
- Go back to the filings afterwards. Index membership changes who owns a stock. It changes nothing on the balance sheet.
For the terminology underneath all of this, see what a microcap stock actually is. For turning a filing into a funding position, see how to calculate cash runway from a 10-Q. The screen we run before covering any name is on our methodology page.
Frequently asked questions
How many stocks are in the Russell Microcap Index?
Roughly 2,000 securities.
The index is built from the smallest 1,000 members of the Russell 2000 plus the next 1,000 eligible securities ranked below them. The exact count moves at each reconstitution as companies are added, removed, delisted, or acquired, so any precise figure is only accurate as of a stated date. Third-party analysis reported 252 additions at the June 2026 reconstitution, which gives a sense of how much turnover a single rebuild can carry.
What stocks are in the Russell Microcap Index?
FTSE Russell publishes the official membership list, and that is the only version worth relying on.
Constituent lists circulate widely in secondary sources and go stale quickly, particularly around reconstitution, when preliminary lists are revised four times before taking effect. Anyone who needs the membership should take it from FTSE Russell directly and note the date it was pulled. Describing the criteria is durable. Reproducing a list of 2,000 names is accurate for about a week.
When is the Russell reconstitution?
Twice a year from 2026, in June and December, having previously been an annual June event.
For the June 2026 cycle, rank day was April 30, preliminary lists were published on May 22 with updates through June 18, and the new membership took effect after the market close on Friday June 26. A second rebalance follows in December 2026, addressing market capitalization changes primarily. FTSE Russell also reviews newly listed companies quarterly in March and September. The move to a semi-annual schedule followed a market consultation, and the stated intent was better representativeness during periods of heightened volatility.
Does joining the Russell Microcap Index mean a company is a good investment?
No. Inclusion is a size ranking that clears a set of mechanical screens, not an assessment of the business.
The screens test exchange, share price, market capitalization, free float, voting rights, and legal structure. A company can satisfy all of them while carrying going-concern language, a rapidly rising share count, or no revenue at all. Inclusion does bring one real change, which is that passive funds tracking the index become holders, and that has effects on liquidity and on the shareholder register. Those are structural facts about the stock rather than facts about the company. Press releases announcing index inclusion are a routine investor-relations exercise and should be read as such.
What is the difference between the Russell Microcap Index and the Russell 2000?
The Russell 2000 is the US small cap benchmark. The Russell Microcap sits below it and overlaps its bottom half.
The Russell 2000 holds companies ranked 1,001 to 3,000 by total market capitalization. The Russell Microcap takes the smallest 1,000 of those and adds the next 1,000 eligible securities below, so the two indexes share 1,000 constituents rather than being mutually exclusive. Combining the Russell 3000 with the Russell Microcap gives the Russell 3000E, covering up to the 4,000 largest US stocks. The upper boundary of the small cap tier gives a sense of the distance involved: the breakpoint separating the Russell 1000 from the Russell 2000 was $5.7 billion at the June 2026 reconstitution.
Disclosure
This article is independent editorial content and reflects the author's opinion and analysis as of the date of publication. It is not investment advice and should not be relied on as the basis for any investment decision. MicroCap Desk and its contributors received no compensation of any kind — cash, securities, or otherwise — from any company mentioned, or from any third party, in connection with this article. The author holds no position in any security mentioned. Information is drawn from sources believed reliable but is not guaranteed accurate or complete. Microcap securities carry a high risk of loss. Do your own research. See our full Disclosure.
