Does the Size Factor (Small Cap Premium) Still Exist?

Is the Idea of Small Stocks Beating Big Stocks a Myth?

Have you ever heard the advice that investing in small companies is the secret to getting rich? For decades, this was a popular belief in the investment world. The idea is called the size factor or the small-cap premium. It suggests that, over the long run, stocks of smaller companies provide better returns than stocks of larger companies. This is a core concept in understanding what is factor investing. But in recent years, this idea has been seriously challenged. So, does the size factor still exist, or is it a relic of the past?

Many people believe that small-cap stocks are a guaranteed way to outperform the market. This belief comes from solid historical data. For much of the 20th century, if you had invested in a basket of small companies, your portfolio would have grown much faster than an investment in large, established companies. But the last decade has told a very different story, leaving many investors wondering if the old rules still apply.

The Case For the Small-Cap Premium

The idea of a small-cap premium isn't just a random observation. It was famously documented by Nobel laureate Eugene Fama and researcher Kenneth French in their groundbreaking Fama-French three-factor model in the 1990s. They showed that, historically, two factors besides overall market risk helped explain stock returns: size and value. Let's look at why the size premium should, in theory, exist.

Why Smaller Companies Might Offer Higher Returns

• Higher Risk: Small companies are generally riskier. They are more vulnerable to economic downturns, have less access to capital, and have a higher chance of failure. To convince investors to take on this extra risk, the market has to offer the potential for higher rewards. This is the classic risk-reward trade-off.
• Greater Growth Potential: A small company has much more room to grow than a corporate giant. A company worth 500 million dollars can realistically double or triple in size. It's much harder for a 2 trillion dollar company to do the same. This high growth potential is a major attraction.
• Less Analyst Coverage: Big, famous companies are followed by hundreds of financial analysts. Small companies are often ignored. This lack of attention can lead to mispricing, where a company's stock is cheaper than it should be. Smart investors can find hidden gems before the rest of the market does.

Example: Imagine two companies. Company A is a huge, stable bank that has been around for 100 years. Company B is a small tech startup with an innovative new product. Investing in Company A is safe, but its growth is likely slow. Investing in Company B is risky — it could fail — but if it succeeds, your investment could grow tenfold. The small-cap premium is the extra return you expect for taking the gamble on Company B.

The Lost Decade: Why People Think the Size Factor is Dead

Despite the strong historical evidence, the last 10-15 years have not been kind to the size factor. Large-cap stocks, especially giant technology companies, have dominated the market. This has led many to declare that the small-cap premium is gone for good. Look at the numbers. The performance gap has been significant.

Comparing Small vs. Large Company Stock Performance

Note: These are illustrative historical figures and not indicative of future results.

So, what happened? Several forces have been working against small caps:

1. The Rise of Mega-Tech: Companies like Apple, Amazon, and Google grew to unprecedented sizes, and their stock performance pulled the entire large-cap segment up with them. Their global reach and dominance were things small companies just couldn't compete with.
2. Globalization: Large multinational corporations were better positioned to benefit from a globalized economy, expanding their markets and supply chains in ways smaller, domestic firms could not.
3. Increased Market Efficiency: The secret is out. Everyone knows about the small-cap premium now. As more investors and funds have poured money into small caps to capture this premium, the potential for outperformance may have been reduced.
4. Low Interest Rates: For much of the last decade, low interest rates made it easy for large, stable companies to borrow money and grow even bigger, while riskier small companies didn't benefit as much.

For more on investment risks and factors, the U.S. Securities and Exchange Commission provides helpful investor resources. You can learn more at their website sec.gov.

The Verdict: Is It Gone for Good or Just Resting?

Declaring the size factor dead might be premature. Investment factors can go through long periods of underperformance. The value factor, for example, also had a terrible decade before recently showing signs of life again. The premium might not be a constant, guaranteed win every year. Instead, it might show up in cycles.

The fundamental logic still holds. Investing in smaller, less stable businesses is riskier than investing in large, established ones. Over a long enough timeline, investors should be compensated for taking that extra risk. What has changed is our understanding of that timeline. It may require more patience than investors in the 20th century needed.

It's also possible the premium is smaller than it used to be. As markets become more efficient, excess returns from simple strategies tend to shrink. The small-cap premium might still exist, but it may be too small to be a reliable cornerstone of a portfolio by itself.

How to Approach Small Caps and Factor Investing Today

So, what should you do? Abandoning small caps entirely is probably an overreaction. A diversified portfolio should ideally include companies of all sizes. The key is to have realistic expectations.

Instead of betting everything on the size factor, a better approach is to see it as one tool among many. This is the core of modern factor investing. You can build a more robust portfolio by combining several factors that have historically shown strong performance. For example, instead of just buying all small-cap stocks, you might look for companies that are both small and have high-quality balance sheets or are trading at a low price (value).

Don't count the little guys out just yet. The size premium may be sleeping, not dead. But waiting for it to wake up requires patience and a strategy that doesn't depend on just one single factor for success.