What Is the S&P 600?

The S&P 600 is an index of small-cap stocks managed by Standard and Poor's. It tracks a broad range of small-sized companies that meet specific liquidity and stability requirements. This is determined by specific metrics such as public float, market capitalization, and financial viability among a few other factors.

Key Takeaways

  • The S&P 600 is a benchmark index for small-cap stocks published by Standard and Poors.
  • Stocks must have market cap of $450 million to $2.10 billion, which also prevents overlap with S&P's larger cap indices.
  • Several index ETFs and mutual funds allow investors to track the performance of the S&P 600 small-cap index.

Understanding the S&P 600

The S&P 600 is comparable to the Russell 2000 Index in that both measure the performance of small-cap stocks but the former covers a much narrower range of assets. For this reason, the S&P 600 only watches about 3-4% of total investable equities in the United States. As of October 2017, there were 601 stocks tracked in the index with an average market capitalization of about $1.36 billion. Market capitalization for inclusion in the S&P 600 small-cap index must fall between $450 million and $2.1 billion to ensure individual assets do not overlap with the larger S&P 500 or mid-cap S&P 400 indexes. 

The top 10% of holdings dictate about 5.2% of all movement in the index. Some of the companies with the largest weighting in the index include Interactive Brokers (IKBR) and Stamps.com (STMP). A breakdown by sector shows a large portion of the listed companies operate in industrials, financials, and information technology. The fewest number of companies do business in telecommunications and consumer staples. 

Investing in the S&P 600

It's not possible to directly buy and sell an index, but several exchange-traded funds (ETF) exist for investors looking to trade the S&P 600. The most active ones flow through Blackrock's iShares (IJR), State Street's SPDR (SLY), and Vanguard (VIOO). One reason investors choose these funds is to capture the massive upside potential offered by small-cap stocks. The truth is that many of the more successful companies leave the benchmark when a spot opens up in one of the larger indexes. Other reasons to leave the index include a merger or de-listing from the stock exchange. 

Limitations of the S&P 600

Investing in small-sized companies may offer higher potential returns than large-cap stocks, but it also presents several challenges. Many of the companies listed on the S&P 600 maintain small geographic footprints and tend to suffer when the dollar weakens. In theory, this provides an incentive to trade overseas rather than to buy from a small, domestically owned business. A hit to earnings growth would likely also take a toll on the stock price. Moreover, many small companies have lower levels of liquidity and higher volatility than a large cap, meaning they tend to fluctuate more erratically.