S&P 400: Your Mid-Cap Market Benchmark

The S&P MidCap 400 Index, commonly known as the S&P 400, is a popular benchmark for mid-cap stocks in the United States. This comprehensive guide will provide an in-depth look at the index, its components, and how it can serve as a valuable tool for investors seeking exposure to the mid-cap segment of the market.

What is the S&P 400?

The S&P MidCap 400 Index, commonly known as the S&P 400, is a stock market index that tracks the performance of mid-cap companies in the United States. Introduced on June 19, 1991 and maintained by Standard & Poor’s, the index offers investors a reliable benchmark for evaluating the mid-cap segment of the U.S. stock market.

Mid-cap companies are typically defined as those with market capitalizations between $2 billion and $10 billion. These companies tend to be more established than small-cap companies but not as large and mature as the large-cap companies. Mid-cap stocks can offer investors a balance of growth potential and stability, as they often have proven business models and experienced management teams, while still having room for expansion and growth.

The S&P 400 is composed of 400 mid-cap companies that are selected by a committee based on various criteria such as market capitalization, liquidity, financial viability, and other factors. The index is designed to provide a comprehensive and representative sample of the mid-cap segment of the U.S. stock market, covering all major sectors including information technology, health care, financials, industrials, consumer discretionary, and others.

The S&P 400 uses a float-adjusted, market capitalization-weighted methodology, which means that the weight of each stock in the index is determined by its market capitalization adjusted for the number of shares available for trading. This approach ensures that the index accurately reflects the overall market value of its constituents.

The index is rebalanced quarterly to account for changes in market capitalization, new listings, or delistings. This regular rebalancing ensures that the index remains a true representation of the mid-cap segment of the U.S. stock market.

Investors can gain exposure to the S&P 400 through various investment vehicles such as exchange-traded funds (ETFs) and mutual funds that track the index. Some popular S&P 400 ETFs include the iShares Core S&P Mid-Cap ETF (IJH) and the SPDR S&P MidCap 400 ETF (MDY).

How to Invest in the S&P 400

Investing in the S&P 400 can be an effective way to gain exposure to the mid-cap segment of the U.S. stock market, offering a balance of growth potential and stability. This guide will discuss various ways to invest in the S&P 400, including exchange-traded funds (ETFs), mutual funds, and individual stock selection, along with the advantages and disadvantages of each approach.

  1. Exchange-Traded Funds (ETFs)

ETFs are one of the most popular ways to invest in the S&P 400. They are investment funds that trade like stocks on stock exchanges and typically aim to replicate the performance of an index by holding the same stocks in the same proportions as the index.


  • Diversification: By investing in an S&P 400 ETF, you gain exposure to all 400 mid-cap stocks in the index, reducing the impact of individual stock performance on your overall returns.
  • Liquidity: ETFs are traded on stock exchanges, making it easy to buy and sell shares throughout the trading day.
  • Cost-efficiency: ETFs generally have lower expense ratios than mutual funds, as they passively track an index and require less active management.
  • Transparency: ETF holdings are disclosed daily, allowing investors to see exactly what they own.

Popular S&P 400 ETFs:

  • iShares Core S&P Mid-Cap ETF (IJH)
  • SPDR S&P MidCap 400 ETF (MDY)
  1. Mutual Funds

Mutual funds are another way to invest in the S&P 400. Like ETFs, mutual funds pool the investments of multiple investors to purchase a diversified portfolio of stocks. However, mutual funds are actively managed, with fund managers making buy and sell decisions in an attempt to outperform the benchmark index.


  • Professional management: Mutual funds are managed by experienced investment professionals who analyze market trends and individual stock performance to make investment decisions.
  • Diversification: Like ETFs, mutual funds provide exposure to a diversified portfolio of stocks, reducing the impact of individual stock performance on overall returns.


  • Higher fees: Actively managed mutual funds typically have higher expense ratios than passively managed ETFs due to the costs associated with active management.
  • Less liquidity: Mutual funds can only be bought or sold at the end of the trading day at the net asset value (NAV) price, limiting flexibility for investors.
  • Potential underperformance: Actively managed funds may underperform their benchmark index due to management fees and the possibility of poor stock selection by the fund manager.
  1. Individual Stock Selection

Investors can also choose to invest in individual mid-cap stocks that are part of the S&P 400. This approach requires a deep understanding of each company’s business, financial health, and growth prospects.


  • Potential for higher returns: By carefully selecting individual stocks, investors may be able to achieve higher returns than the overall index.
  • Customization: Investors can tailor their portfolio to their specific investment objectives and risk tolerance by selecting individual stocks.


  • Risk of underperformance: Picking individual stocks carries the risk of underperformance if the chosen stocks do not perform well.
  • Time-consuming: Researching and analyzing individual stocks requires significant time and effort.
  • Less diversification: Investing in a smaller number of individual stocks reduces diversification, increasing the potential impact of individual stock performance on overall returns.

Each investment approach has its advantages and disadvantages. ETFs offer diversification, liquidity, cost-efficiency, and transparency, making them a popular choice for many investors. Mutual funds provide professional management and diversification but may come with higher fees and less liquidity compared to ETFs. Individual stock selection allows for customization and the potential for higher returns, but it can be time-consuming and carries the risk of underperformance and reduced diversification.

Ultimately, the most suitable approach to investing in the S&P 400 will depend on your individual investment goals, time horizon, and risk tolerance. It is essential to carefully consider your options and, if necessary, consult with a financial advisor to help you make the best decision for your investment portfolio.

Annual Returns of the S&P 400

Since its inception, the S&P MidCap 400 Index has provided investors with a reliable benchmark for the performance of mid-cap stocks in the United States. This section examines the annual returns of the S&P 400 since its inception, highlighting the index’s performance over time.

It is important to note that historical performance is not indicative of future results, and past returns should not be used as the sole basis for making investment decisions. However, analyzing the S&P 400’s historical returns can offer insight into the index’s overall performance and how it has fared during different market conditions.

The annual returns of the S&P 400 have varied widely over the years, with periods of strong performance as well as years with negative returns. The index has experienced significant gains during bull markets, such as the late 1990s and the period following the 2008 financial crisis. Conversely, it has seen declines during periods of economic downturn, such as the dot-com crash in the early 2000s and the Great Recession in 2008.

While it is difficult to provide a detailed account of the annual returns for each year since the index’s inception, the average annual return for the S&P 400 from 1991 to 2021 is approximately 11.5%. This figure highlights the index’s long-term growth potential and underscores the importance of mid-cap stocks in a well-diversified investment portfolio.

In conclusion, analyzing the annual returns of the S&P 400 since its inception can provide valuable insights into the index’s performance and the role of mid-cap stocks in the U.S. stock market. While historical returns should not be the sole basis for making investment decisions, understanding the index’s past performance can help investors make informed decisions about incorporating the S&P 400 into their overall investment strategy.