Direct Answer
The Russell 2500 Index, also called the SMID index, measures the performance of the 2,500 smallest stocks in the Russell 3000 universe. It combines the Russell 2000 small-cap universe with the 500 smallest stocks from the Russell 1000 mid-cap tier. FTSE Russell administers the index using float-adjusted market-cap weighting and reconstitutes it annually in June alongside the broader Russell family.
What SMID Means
SMID is a compound abbreviation standing for small and mid-cap. It describes a market segment that sits below the largest-cap stocks and above the micro-cap tier, blending what are typically classified as small and mid-cap companies into a single unified exposure. Investment professionals use the SMID label when they want to discuss or invest in this combined portion of the market without separating it into pure small-cap and pure mid-cap components.
The Russell 2500 is one of the most established SMID benchmarks in the U.S. equity market. It captures what many practitioners regard as the most economically dynamic segment of the public equity market: companies that are large enough to have meaningful operating scale and analyst coverage, but small enough that their growth trajectories are not yet fully priced with the precision typically applied to mega-cap stocks. Companies in this size range are often in earlier stages of market leadership in their respective industries.
The SMID designation carries specific meaning in portfolio construction as well. Some institutional investors maintain SMID allocations as a distinct bucket rather than separate small-cap and mid-cap allocations, reasoning that the two segments share enough characteristics in terms of analyst coverage, liquidity profiles, and factor exposures to be managed together. The Russell 2500 provides an off-the-shelf benchmark for such strategies.
How the Russell 2500 Relates to the Russell 1000 and Russell 2000
The Russell 3000 serves as the master universe from which all Russell US size indexes are derived. It aims to capture approximately the largest 3,000 eligible U.S. companies by total market capitalization. From this universe, the top 1,000 companies by market cap form the Russell 1000, and the bottom 2,000 form the Russell 2000. The two sub-indexes are mutually exclusive and together account for all Russell 3000 constituents.
The Russell 2500 takes a different cut through the same universe. Rather than starting from the bottom of the Russell 3000, it takes the bottom 2,500 stocks: the full Russell 2000 plus the 500 smallest stocks from within the Russell 1000. Those 500 stocks from the Russell 1000 represent the lower portion of the large-cap or mid-cap tier depending on how one defines those categories. FTSE Russell refers to these as the mid-cap segment in the context of the Russell 2500.
Because the Russell 2500 includes companies from two different parent indexes (Russell 2000 and Russell 1000), it overlaps with both but is identical to neither. An investor holding the Russell 2500 has exposure to all Russell 2000 companies plus a mid-cap supplement that other pure small-cap indexes do not include. This overlap structure means that performance differences between the Russell 2500 and the Russell 2000 are driven entirely by the behavior of those 500 mid-cap additions, since the small-cap portion is identical.
Float-Adjusted Market-Cap Weighting
FTSE Russell weights each Russell 2500 constituent by its float-adjusted market capitalization rather than its total market capitalization. Float adjustment excludes shares that are not freely available for public trading, including shares held by corporate insiders above certain ownership thresholds, shares owned by governments, cross-holdings between companies, and shares subject to lock-up restrictions. The resulting float-adjusted weight reflects what is actually investable by public market participants rather than the full theoretical market value of the company.
Float adjustment is particularly relevant in the small and mid-cap space because insider ownership rates can be higher among smaller companies, especially those that are still founder-led or have significant institutional anchor investors. A company with a large total market cap but a small public float will have a lower weight in the Russell 2500 than its raw size would suggest. This reduces the index's exposure to concentration risk from tightly held companies whose float is thin relative to their total valuation.
The float adjustment factors are reviewed at the annual reconstitution and may also be updated between reconstitutions when significant changes in share structure occur, such as a secondary offering that substantially increases the public float or a buyback program that reduces shares outstanding. FTSE Russell publishes the methodology governing how these adjustments are calculated and applied.
Annual June Reconstitution
Like all Russell US indexes, the Russell 2500 is reconstituted annually each June. The process begins with a re-ranking of all eligible U.S. companies in the Russell 3000 universe by total market capitalization as of a specified rank date. Companies that have grown above the Russell 1000 cutoff migrate out of the Russell 2500's mid-cap supplement and into the top 500 of the Russell 1000 (and thus out of the Russell 2500). Companies that have grown enough to enter the mid-cap tier for the first time are added to the supplement. The Russell 2000 membership changes simultaneously drive the small-cap portion of the index.
The reconstitution effective date is typically the last Friday of June, and FTSE Russell publishes advance notice of provisional membership changes in the weeks preceding that date. This advance notice is important for funds that track the Russell 2500, because the index covers a large number of stocks across the small and mid-cap size spectrum, and the associated trading to rebalance index-linked products can be substantial in aggregate, particularly for smaller and less liquid constituents.
Quarterly additions of newly public companies are possible between annual reconstitutions. IPOs and other newly listed companies that meet the eligibility and size requirements at a quarterly review date can be added to the Russell 2500 without waiting until the next June reconstitution. This feature keeps the index current with new entries to the investable universe, which is particularly relevant in the small and mid-cap space where IPO activity regularly introduces companies of meaningful size.
Comparing the Russell 2500 and the Russell 2000
The Russell 2000 is a pure small-cap index, capturing the bottom 2,000 stocks in the Russell 3000 with no mid-cap component. The Russell 2500 extends upward by adding the 500 smallest members of the Russell 1000, giving it a broader size range. Because the small-cap portion is identical between the two indexes, any performance difference between them reflects purely the performance of the mid-cap supplement in the Russell 2500.
The average company size in the Russell 2500 is larger than in the Russell 2000 because the mid-cap additions are by definition bigger than any Russell 2000 constituent. This size difference has practical implications: the mid-cap stocks in the Russell 2500 tend to be more liquid, have more analyst coverage, and are less sensitive to small-cap-specific risk factors such as microstructure frictions. Adding them moderates the pure small-cap volatility of the Russell 2000, though the Russell 2500 still carries substantially higher volatility than large-cap benchmarks.
For investors who want to track or benchmark against the small-cap segment but find the pure Russell 2000 too volatile or too illiquid in aggregate, the Russell 2500 offers a middle ground. For those conducting academic or factor research on the size premium, the Russell 2500 and Russell 2000 can be compared directly to isolate the marginal contribution of the mid-cap tier to returns and risk characteristics.
Comparing the Russell 2500 and the Russell 1000
The Russell 1000 covers the largest 1,000 stocks in the Russell 3000, while the Russell 2500 covers the smallest 2,500. The two indexes share no constituents: every stock is either in one or the other, and together with the remainder of the Russell 3000 they cover the full eligible universe. Investors comparing these two indexes are comparing very different segments of the market in terms of company size, liquidity, and factor exposures.
The Russell 1000 is dominated by mega-cap and large-cap companies. Its float-adjusted market cap weighting means that a small number of very large companies account for a disproportionate share of the index's total weight. The Russell 2500, by contrast, has far more equal weight distribution because the size range of its constituents is compressed: no single stock in the Russell 2500 can be as dominant as the largest members of the Russell 1000.
Return differences between the two indexes over time reflect the well-documented size premium research in academic finance, as well as cyclical forces that drive large-cap leadership versus small and mid-cap leadership over different periods. In general, the Russell 2500 has historically exhibited higher volatility than the Russell 1000, consistent with the higher fundamental uncertainty and lower liquidity of smaller companies. However, periods of small and mid-cap leadership can produce extended stretches of outperformance for the Russell 2500 relative to large-cap benchmarks.
Comparing with the S&P MidCap 400 and S&P SmallCap 600 Combined
The S&P MidCap 400 and S&P SmallCap 600 indexes together cover a similar size range to the Russell 2500, but they use a fundamentally different construction methodology. The S&P indexes are committee-selected, meaning a group of professionals at S&P Dow Jones Indices reviews and approves each addition based on criteria that include profitability (positive earnings over four consecutive quarters), a minimum liquidity ratio, and adequate public float. The Russell 2500, by contrast, is mechanically constructed from a market-cap ranking without a selection committee or profitability screen.
The profitability screen is the most consequential methodological difference. Many small-cap companies are unprofitable, particularly in sectors like biotechnology and early-stage technology where companies invest heavily in research and development before reaching operating profitability. These companies can qualify for the Russell 2500 based on size alone, but they would not qualify for the S&P SmallCap 600 until they achieve the earnings threshold. As a result, the S&P combination tends to have a stronger quality tilt and somewhat different sector composition than the Russell 2500.
Both approaches have their advocates. The Russell 2500's exhaustive coverage without a profitability screen means it captures the full opportunity set of publicly traded small and mid-cap companies, including pre-profitable growth companies. The S&P combination's profitability screen excludes some of the highest-risk constituents, which can reduce volatility but may also exclude some of the highest-return components during periods when early-stage companies outperform. The choice between them depends on the investor's objectives and views about the profitability factor.
Sector Exposure
The sector composition of the Russell 2500 reflects the combined characteristics of both the small-cap and mid-cap segments of the U.S. equity market. Because the index spans a wider size range than a pure small-cap index, its sector mix tends to be more diversified than the Russell 2000 alone. Mid-cap companies across various sectors contribute sector exposures that may be underrepresented in the pure small-cap universe, particularly in capital-intensive industries where minimum scale matters for operational viability.
Financials, industrials, health care, information technology, and consumer discretionary have historically been significant sectors within the Russell 2500, though the precise weights shift with each annual reconstitution based on company size changes and the IPO pipeline in each sector. The absence of a sector constraint or target means the index can develop meaningful sector tilts over time, particularly if a dominant theme in the IPO market (such as biotech or technology platform companies) concentrates new additions in one sector.
Investors using the Russell 2500 as a benchmark should review current sector composition data published by FTSE Russell rather than relying on historical averages. Sector weights can shift between reconstitutions when a particular sector experiences valuation changes that affect the relative size ranking of its companies within the Russell 3000 universe.
Return Variants
FTSE Russell publishes the Russell 2500 in price return, total return, and net total return variants, consistent with the broader Russell US index family. The price return reflects stock price changes only. The total return reinvests dividends at the ex-dividend date. The net total return adjusts for dividend withholding taxes applicable to non-U.S. investors.
Because the Russell 2500 spans both small-cap companies that often pay no dividends and mid-cap companies that more frequently pay dividends, the spread between price return and total return varies depending on the dividend behavior of the current constituents. Researchers comparing the Russell 2500 to the Russell 2000 over long periods should use consistent return variants across both indexes to avoid measuring a dividend-yield difference as a performance difference.
Style sub-indexes, namely the Russell 2500 Growth and Russell 2500 Value, are also maintained by FTSE Russell using the same composite growth and value scoring methodology applied across the broader Russell family. These sub-indexes allow investors to separate style tilts within the SMID segment in the same way that the Russell 2000 Growth and Value sub-indexes separate style within pure small-cap.
Frequently asked questions
What does SMID mean in reference to the Russell 2500?
SMID stands for small and mid-cap, a term used to describe the market segment that blends small-cap and mid-cap stocks. The Russell 2500 is often called a SMID index because it includes both the full Russell 2000 small-cap universe and the 500 smallest stocks from the Russell 1000 mid-cap tier, spanning both size categories in a single index.
How is the Russell 2500 constructed?
The Russell 2500 consists of the 2,500 smallest companies in the Russell 3000 by float-adjusted market capitalization. It combines all members of the Russell 2000 small-cap index with the 500 smallest members of the Russell 1000, which represents the mid-cap segment. FTSE Russell weights each constituent by float-adjusted market capitalization.
How does the Russell 2500 differ from the Russell 2000?
The Russell 2000 contains the bottom 2,000 stocks in the Russell 3000 by market capitalization and is a pure small-cap index. The Russell 2500 adds the 500 smallest stocks from the Russell 1000 to extend the size range upward into mid-cap territory. The result is a broader index that captures both small and mid-sized companies, giving it a somewhat larger average market capitalization than the Russell 2000 alone.
When is the Russell 2500 reconstituted?
FTSE Russell reconstitutes the Russell 2500 each June as part of its annual Russell US index reconstitution process. Membership changes take effect at the end of June. Between annual reconstitutions, newly listed companies that meet size and eligibility requirements can be added on a quarterly basis.
How does the Russell 2500 compare with combining the S&P MidCap 400 and S&P SmallCap 600?
Both approaches aim to capture the mid and small-cap segment of the U.S. equity market, but they differ in methodology. The Russell 2500 uses a rules-based, exhaustive ranking of the Russell 3000 universe without a selection committee. The S&P MidCap 400 and SmallCap 600 each involve committee-based selection with profitability and liquidity screens. The two combinations will overlap substantially in holdings but will differ at the margins based on these methodology differences.