The S&P 500 Is Doing Something That Hasn't Been Seen in Nearly 100 Years. Here Are the 10 Most Important Stocks to Keep an Eye On.

Adam Spatacco, The Motley Fool

Tue, Apr 29, 2025, 6:30 AM 5 min read

An interesting psychological aspect of stock market dynamics is that investors often fall into the trap of viewing times of favorable or unfavorable conditions through a binary lens. What I mean by that is it's not uncommon for investors to follow the herd and recency bias when picking and choosing stocks.

Several eye-opening trends are fueling the movements across the S&P 500 (SNPINDEX: ^GSPC) right now. What's going on in the index can be tied to the phenomena above to help shed some light on what stocks investors should keep a close eye on as the market swings from one extreme to another.

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According to a research report published by investment bank Goldman Sachs, concentration levels within S&P 500 are hovering around their highest levels in 93 years.

According to Goldman, concentration levels of this magnitude have occurred eight times during the past century: 1932, 1939, 1964, 1973, 2000, 2009, 2020, and now. As the data in the report shows, the weight of the top 10 stocks in the S&P 500 is nominally higher than ever.

Goldman's analysis is pretty interesting, but as an investor my guess is you're wondering which stocks are actually having the most influence on the S&P 500's movements right now. As of April 24, the top 10 stocks in the S&P 500 weighted by market cap are:

1. Apple: $3.1 trillion

2. Microsoft: $2.9 trillion

3. Nvidia: $2.6 trillion

4. Amazon: $1.9 trillion

5. Alphabet: $1.9 trillion

6. Meta Platforms: $1.3 trillion

7. Berkshire Hathaway: $1.1 trillion

8. Broadcom: $880 billion

9. Tesla: $826 billion

10. Eli Lilly: $770 billion

With the exception of Berkshire and Lilly, each of the stocks cited above is underperforming the S&P 500 so far this year as of this writing.

There are a couple of different ideas I'd like to unpack given the data and these specific stocks.

First, it's not entirely surprising to see such a precipitous drop in high-growth technology stocks such as the "Magnificent Seven." Thanks to the bullish narratives fueling artificial intelligence (AI), investors have been flocking in droves (herd mentality) to invest in megacap tech stocks during the past couple of years. This has resulted in an unprecedented run for most of big tech. But during times of economic uncertainty (like now), it's not uncommon for investors to take some gains off the table and reallocate funds into consumer defensive stocks, index funds, commodities such as gold, or dividend stocks.