S&P 600
What Is the S&P 600?
The S&P 600 is a stock market index maintained by Standard & Poor's that tracks the performance of 600 small-capitalization companies in the United States, serving as a benchmark for the small-cap sector.
The S&P SmallCap 600 (often just called the S&P 600) is an index designed to measure the performance of the small-capitalization segment of the U.S. equity market. Launched in 1994, it serves as a counterpart to the S&P 500 (large-cap) and S&P 400 (mid-cap). Together, these three indices make up the S&P 1500, covering roughly 90% of the U.S. market capitalization. Unlike broad-market indices that blindly include every company of a certain size, the S&P 600 is curated by a committee. This committee ensures that the index represents a diverse range of sectors and that the companies included are financially viable. This "human touch" distinguishes it from its main competitor, the Russell 2000, which uses a purely mathematical rule to include the bottom 2,000 stocks of the Russell 3000. While the Russell 2000 is more famous, the S&P 600 is widely considered a superior benchmark for "quality" small-cap exposure. By filtering out unprofitable companies, it avoids much of the speculative excess that can plague the small-cap space, offering a cleaner view of the health of established, albeit smaller, American businesses. It provides a more accurate reflection of the investable small-cap universe rather than just a catch-all for every tiny public company.
Key Takeaways
- The S&P 600 covers approximately 3-4% of the U.S. equities market, focusing on the small-cap segment.
- It requires companies to have positive earnings for the most recent quarter and the sum of the last four quarters, adding a quality filter not found in other small-cap indices.
- Constituents must have a market capitalization between $850 million and $3.7 billion (thresholds vary over time).
- It is often compared to the Russell 2000, but the S&P 600 generally outperforms over the long term due to its profitability requirements.
- The index is float-adjusted and market-capitalization-weighted.
- Investors use it to gain exposure to the higher growth potential of smaller companies, though with higher volatility.
How the S&P 600 Works
To be included in the S&P 600, a company must meet specific criteria regarding liquidity, public float (percentage of shares available for trading), and financial health. The most critical requirement is profitability: a company must report positive earnings in its most recent quarter, and the sum of its earnings over the last four quarters must also be positive. This profitability filter is a game-changer. It excludes speculative "zombie companies" or early-stage firms that are burning cash—types of stocks often found in other small-cap indices. As a result, the S&P 600 has historically exhibited slightly less volatility and better long-term returns than the Russell 2000, which includes many unprofitable companies. Like the S&P 500, the S&P 600 is capitalization-weighted. This means that within the index, larger small-cap companies (those closer to the $3-4 billion range) have a bigger impact on the index's daily moves than the smaller ones (those closer to $800 million). The index is also float-adjusted, meaning that closely held shares by insiders or governments are excluded from the weighting calculation. This ensures that the index reflects the actual tradable opportunity set available to investors.
S&P 600 vs. Russell 2000
The battle of the small-cap benchmarks is a common topic for portfolio managers.
| Feature | S&P 600 | Russell 2000 | Key Difference |
|---|---|---|---|
| Selection Method | Committee + Profitability Rules | Pure Market Cap Rank | S&P 600 filters for quality. |
| Profitability | Must be profitable | No requirement | S&P 600 avoids money-losing firms. |
| Rebalancing | As needed (ongoing) | Annual (June) | S&P 600 is more dynamic. |
| Performance | Historically higher | Historically lower | Quality filter tends to outperform. |
| Popularity | Less tracked by ETFs | Most tracked by ETFs | Russell 2000 is the standard benchmark despite lower quality. |
Advantages of the S&P 600
Investing in the S&P 600 offers exposure to the "small-cap premium"—the historical tendency for smaller, nimbler companies to grow faster than massive conglomerates. Small caps are often the target of mergers and acquisitions, which can lead to quick price jumps for shareholders. Furthermore, the S&P 600's quality screen makes it a "safer" way to play the risky small-cap market. By filtering out companies that are losing money, investors get the growth potential of small businesses without as much exposure to the highest-risk speculative stocks.
Disadvantages and Risks
Small-cap stocks are inherently more volatile than large caps. During economic downturns, small companies often have weaker balance sheets and less access to credit, making them more vulnerable to bankruptcy. The S&P 600 will almost always fall harder than the S&P 500 during a recession. Additionally, while the profitability rule is a strength, it can also be a weakness in speculative bull markets. The index might miss out on the explosive early growth of a pre-profit tech unicorn that would be included in the Russell 2000. Finally, there are fewer ETFs and mutual funds tracking the S&P 600 compared to the S&P 500 or Russell 2000, potentially leading to slightly higher expense ratios or lower liquidity for the funds themselves.
Real-World Example: "Graduating" Companies
The S&P indices function like a league system.
FAQs
You can buy ETFs that track the index. Popular options include the iShares Core S&P Small-Cap ETF (IJR), the SPDR S&P 600 Small Cap ETF (SLY), and the Vanguard S&P Small-Cap 600 ETF (VIOO). These funds hold all or most of the stocks in the index, giving you instant diversified exposure to high-quality U.S. small caps.
The sector weighting is more balanced than the tech-heavy S&P 500. Industrials, Financials, and Consumer Discretionary sectors often make up a large portion of the index, reflecting the domestic focus of many small businesses. Technology is present but less dominant than in large-cap indices.
It depends on your goal. Over very long periods (20+ years), small caps have historically outperformed large caps, but with much higher volatility and deeper drawdowns. The S&P 500 is better for stability and consistent dividends, while the S&P 600 is better for aggressive growth in a diversified portfolio.
In the large-cap world, almost every company is profitable. In the small-cap world, many public companies are "concept stocks" or failing businesses. By requiring profitability, the S&P 600 avoids the "junk" that drags down the returns of broader indices like the Russell 2000.
Changes can happen at any time but are often announced a few days in advance. The index is rebalanced quarterly to adjust share counts and weights, but companies can be added or removed whenever necessary—for example, due to a merger, bankruptcy, or "graduation" to a larger index.
The Bottom Line
The S&P 600 is arguably the "smartest" way to invest in U.S. small-cap stocks. By combining the growth potential of smaller companies with a strict quality filter that demands profitability, it offers a compelling alternative to broader, "junkier" indices like the Russell 2000. While small-cap stocks inherently carry more risk and volatility than their large-cap cousins in the S&P 500, the S&P 600 minimizes this risk by excluding financially distressed firms. For investors with a long time horizon and a tolerance for market swings, adding an allocation to the S&P 600 can boost overall portfolio returns through exposure to the dynamic engine of the American economy—its small businesses.
More in Stock Market Indices
At a Glance
Key Takeaways
- The S&P 600 covers approximately 3-4% of the U.S. equities market, focusing on the small-cap segment.
- It requires companies to have positive earnings for the most recent quarter and the sum of the last four quarters, adding a quality filter not found in other small-cap indices.
- Constituents must have a market capitalization between $850 million and $3.7 billion (thresholds vary over time).
- It is often compared to the Russell 2000, but the S&P 600 generally outperforms over the long term due to its profitability requirements.