The widely followed Standard & Poor’s 500 Index is the standard by which stock market performance in the U.S. is often measured, as it tracks 500 of the largest and most stable publicly traded companies in the country. The index is weighted by market capitalization, which gives more significance to companies with larger market values. The top 25 stocks in the S&P 500 by weight are the largest, most influential companies in the index.

Key Takeaways

• The S&P 500 is widely considered to be one of the best measures of stock market performance and the health of the U.S. economy.
• The 500 stocks tracked by the index represent the nation’s largest, most economically significant companies
• The S&P 500 is weighted by market cap. The larger the company, the more influence its stock price has on the overall index.
• The top 25 stocks in the index are important to follow because of their strong influence on the performance of the index and the economy at large.

As of April 27, 2025, the S&P 500 index was down 6.3% since the beginning of the year, as increasing uncertainty about the effects of President Donald Trump’s tariffs created fears of a recession. Federal Reserve Board Chair Jerome Powell said on April 16 that the Fed will wait for “greater clarity” before making any changes in interest rates. “Unemployment is likely to go up as the economy slows, in all likelihood, and inflation is likely to go up as tariffs find their way and some part of those tariffs come to be paid by the public,” he said.

How are Stocks Selected for the S&P 500?

To be included in the S&P 500, a company must:

• Be based in the United States and trade publicly on a major U. S. exchange
• Maintain a market capitalization of $20.5 billion and a float-adjusted market cap of at least 50% of the index’s total company-level minimum market capitalization threshold
• Have reported positive earnings in the most recent quarter, along with the past four consecutive quarters
• Have a float-adjusted liquidity ratio of 0.75 or greater.
• Have traded a minimum of 250,000 shares in the previous six months before evaluation

The S&P 500 reconstitutes each June. Companies removed from the index are not replaced until the next annual reconstitution.

Top Sectors in the S&P 500

The table below lists the S&P 500’s top sectors by weighting as of April 27, 2025. The information technology, financials, health care, and consumer discretionary sectors carry a cumulative weight of 66.74%. Meanwhile, the least-weighted sectors include energy, utilities, and real estate, which have a combined weight of just 8.64%.

Top 25 Companies by Index Weight

These are the top 25 companies by index weight. Since the S&P Global website does not disclose the weighting of component stocks, we used the S&P 500 exchange-traded fund (ETF), the SPDR S&P 500 ETF Trust (SPY), in order to cite index weighting. The ETF’s holdings are a bit different, but SPY closely reflects the S&P 500 weights.

As of April 27, 2025, here are the largest SPY holdings by weight:

Why Are the S&P 500’s Top 25 Stocks Important?

The top 25 stocks in the S&P 500 by index weight are important to analyze because they can be used to gauge the health of the stock market and broader economy. These companies reflect the performance of key sectors and the benchmark itself.

The current period of outperformance by the technology sector, for example, shows how declining inflation, strong margins, and competitive positioning resulting in good cash flow can contribute to gains in the overall index.

How Do I Invest in the S&P 500 Index?

The simplest and easiest way to invest in the S&P 500 is to purchase the popular SPDR S&P 500 ETF (SPY), which reflects the minute-by-minute movements of the index. Other ETFs that also track the S&P 500 this way include the iShares Core S&P 500 ETF (IVV) and Vanguard S&P 500 ETF (VOO).

There are also index funds that reflect only the closing price at the end of the day, including the Vanguard 500 Index Fund (VFIAX) and Fidelity 500 Index Fund (FXAIX). For those interested in more complex strategies, options and futures are also available, such as E-mini S&P Futures contracts, although these are only for those wishing to speculate on the future value of the index.

Advantages and Disadvantages of Investing in the S&P 500 Index

The central advantage of investing in the S&P 500 is the wide diversification it offers across many sectors and industries. By investing in the index, an investor generally reduces the risk associated with buying individual stocks. Over the years, an investment in the S&P 500 can produce long-term growth for those willing to wait out the accompanying short-term volatility.

A disadvantage of S&P 500 investing is how concentrated the index is in the top-performing stocks, a factor that sometimes skews results and can result in increased volatility. Some investors prefer an S&P 500 Equal Weight Index, where each component has an equal weight without regard to the size of its market capitalization.

The Bottom Line

The S&P 500 index weights companies according to their market caps. Larger firms are more heavily weighted than small firms, which carries some risks. The tech sector, which includes giants like Apple, Microsoft, and Nvidia, has an enormous influence on index results. In general, the stock market’s health and that of the U.S. economy can be measured by analyzing the S&P 500’s top 25 components.

The comments, opinions, and analyses expressed on Investopedia are for informational purposes only. Read our warranty and liability disclaimer for more info. As of the date this article was written, the author does not own any of the above securities.

These are the best undervalued stocks to keep an eye on this month

Value investors seek stocks that are trading on the market at a price point below their fundamental value. These stocks typically represent high-quality companies that are either emerging or whose shares have otherwise fallen. While it can be difficult to execute successfully, value investing allows investors to buy stocks at a relatively low price point and then benefit when the market eventually corrects itself and the price rises to be more in line with the company’s underlying value.

In May 2025, some candidates for value investors to watch include real estate investment trust SITE Centers Corp. (SITC), global shipping firm ZIM Integrated Shipping Services Ltd. (ZIM), and healthcare firm Agios Pharmaceuticals Inc. (AGIO), among others.

Key Takeaways

• Undervalued stocks on the NYSE and the Nasdaq for this month have 12-month trailing P/E ratios as low as 0.52.
• Value investors believe it is possible to identify companies with shares trading below their fundamental value. Later, when the market corrects this pricing error, investors achieve gains as share prices rise.
• P/E ratio is a key metric used to identify value stocks, but this figure can vary significantly from one sector or industry to the next.
• For this reason, it’s most helpful to compare potential value plays against other peers in the same sector.
• Other common value metrics include forward P/E ratio, price-to-book ratio, and price/earnings-to-growth ratio.

Below, we consider some of the top undervalued stocks for this month, as measured by 12-month trailing price-to-earnings (P/E) ratio. A detailed explanation of our methodology is found below. All data are as of April 24, 2025.

Why Are These the Top Undervalued Stocks?

Our screen for the best undervalued stocks includes firms listed on either the New York Stock Exchange (NYSE) or the Nasdaq and with a price of at least $5 per share, a daily trading volume of 100,000 or more, and a market capitalization of $300 million or more. From that list, we ranked the companies in our screen by 12-month trailing P/E ratio and then selected the stock with the lowest P/E ratio from each sector.

While there are many different metrics used in value investing, P/E ratio is one of the most common. It is a measure of the price of a company’s shares against its earnings. A low P/E ratio often suggests that a firm’s recent earnings have performed well relative to its price, meaning that it is undervalued in the market.

When looking for undervalued stocks, investors should keep in mind that P/E ratio is just one of many measures of a company’s value. It’s important to look at the firm’s financials as well as other metrics like P/S ratio (for firms that have yet to achieve profitability), price-to-book ratio, and price/earnings-to-growth ratio for a fuller picture. That said, it is also inherently difficult to calculate a company’s intrinsic value, and market unpredictability means that even legitimately undervalued firms may never see a stock price increase in the future.

What Should Investors Look for in Undervalued Stocks?

While we looked at trailing P/E ratio in our screen, forward P/E ratio is also a helpful metric to use to identify undervalued stocks. The forward P/E ratio makes use of Wall Street analyst predictions of a company’s future earnings. It can be a helpful way to take stock of how developments on the horizon could impact the company’s performance, although it’s also important to note that forward P/E ratio is intrinsically speculative.

Another way of comparing price and earnings is the price/earnings-to-growth ratio, which also includes an estimate of future earnings growth. This may provide investors with a better sense of how a company is likely to fare with regard to future earnings, as well as whether the firm may be undervalued relative to potential earnings growth.

Price-to-book ratio is a measure of a company’s share price against its net value (assets less liabilities). By looking at the firm’s book value per share, investors can get a fuller view of a company’s financial wellbeing. The price-to-book ratio suggests how much investors may be willing to pay for each dollar of the company’s net value.

Finally, regardless of which metrics one uses to evaluate a company, it’s essential to consider a benchmark. When it comes to value investing, it’s impossible to determine whether a company is undervalued unless one has a sense of how it compares to peers in its industry or sector. Because P/E ratios differ significantly from one sector to another, this information helps investors make the most educated guesses possible about a company’s underlying value.

The Bottom Line

Undervalued companies may have the potential to experience outsized returns if the market corrects the price to more closely match their underlying value. Investors seeking a value play might look to metrics like 12-month trailing P/E ratio as one indicator. Our screen has revealed a selection of stocks across sectors that could be undervalued, although there is no guarantee that investors in these stocks will achieve better-than-expected results.

The comments, opinions, and analyses expressed on Investopedia are for informational purposes only. Read our warranty and liability disclaimer for more info.

As of the date this article was written, the author does not own any of the above stocks.