Small-Cap Stock

A small-cap stock is a share of common stock in a company whose market capitalization, its share price multiplied by its shares outstanding, places it at the smaller end of the public market. The security is ordinary common stock and carries the same rights as any other; only the size of the issuer differs.

The boundary is the part worth being careful about, and FINRA is unusually direct about it. Its investor education states: "There are no fixed cutoff points for large-, mid- or small-cap companies, but you might see a small-cap company valued at less than $2 billion, mid-cap companies between $2 billion and $10 billion, and large-cap companies over $10 billion—or the numbers might be twice those amounts." A self-regulatory organization giving the conventional figures and its own warning that they are unreliable, in one sentence, is the most accurate statement available. The SEC's investor glossary has no entry for the category at all.

Index providers commonly avoid the dollar problem by not using dollars. Rather than fixing a boundary, a provider can define a size segment as a share of a market's total value. MSCI's Emerging Markets index, for example, "captures large and mid cap representation" across the countries it covers and reaches "approximately 85% of the free float-adjusted market capitalization in each country," which means the companies below that line are what the segment excludes. Defined that way, the boundary is different in every country, it moves as prices move, and it never needs revising as markets grow. The practical consequence is that a fund's own documents, not a dollar figure, determine what it means by small.

The consequence of a floating convention is that the same company can be labeled two ways at once, by two sources both using the ordinary meaning of the words. That is not sloppiness. It is what "no fixed cutoff points" means in practice, and it is a reason to read a fund's index rather than its name.

Where the additional risk comes from, stated structurally rather than statistically. Smaller companies are typically less diversified across products, customers and regions, so a single lost contract or a single regulatory decision can matter to the whole business. They generally have narrower access to capital, which makes a downturn harder to fund through. Their shares trade less, so the gap between the price at which shares can be bought and the price at which they can be sold tends to be wider, which is a real cost paid twice on every round trip. And fewer analysts follow them, which is simultaneously the argument for the category, since less-examined companies are more likely to be mispriced, and the reason the information a buyer is working from is thinner.

Smaller still. FINRA notes that "you might also hear about micro-cap companies, which are even smaller than other small-cap companies," and elsewhere describes microcap securities as sometimes being referred to as penny stocks. The terms overlap loosely in ordinary use, and the reporting and liquidity concerns at that end of the market are their own subject.

What a small-cap fund is actually doing to a portfolio. A broad cap-weighted fund covering the whole market already holds small companies, at the weight the market assigns them, which is a small weight precisely because they are small. Adding a dedicated small-cap fund does not add a missing exposure. It deliberately holds more of that exposure than the market does, which is an active decision and requires a reason beyond wanting to be diversified. Whether small companies compensate holders for their extra risk over long periods is a contested question in the research literature, and no claim about it belongs on either side of that decision.

A data provider or an index provider computes each company's market capitalization, ranks the market, and draws a line. Where the line falls depends on whose convention is being used, and a fund tracking a small-cap index holds whatever sits below its provider's line at each reconstitution.

A hypothetical example of what "no fixed cutoff points" costs in practice. A company has a market capitalization of $3 billion. Measured against the first set of figures FINRA cites, small below $2 billion and mid from $2 billion to $10 billion, the company is a mid-cap. Measured against the doubled version FINRA says you might equally see, small below $4 billion and mid from $4 billion to $20 billion, the same company is a small-cap.

Nothing about the business changed and neither source is wrong. So an investor who owns a small-cap fund and a mid-cap fund from two different providers can hold the same company twice, or miss it entirely, purely because of where each provider drew its line. The fix is to read which index each fund tracks rather than to compare the words on the labels. All figures are illustrative.

Pros

• Fewer analysts follow these companies, so there is more room for a price to be wrong in either direction.
• Small companies are the part of the market a large-company index such as the S&P 500 leaves out entirely, so this is where breadth beyond it comes from.
• A company that grows substantially has to start somewhere, and the growth happens while it is still small.
• Broad small-cap index funds hold hundreds or thousands of these companies, which removes the risk that any one failure matters much.

Cons

• There is no agreed boundary, so two funds using the same word can hold different companies.
• Shares trade less, so the gap between buying and selling prices is typically wider and is paid on both ends of every trade.
• Smaller companies are usually less diversified across products and customers and have narrower access to capital, so trouble is harder to absorb.
• Thinner analyst coverage means less independent information for a buyer to work from.
• A total-market fund already holds these companies at market weight, so a separate fund is a deliberate overweight rather than an added exposure.