Summer 2025 Snapshot of the S&P 500's Market Cap

The market capitalization of the S&P 500 (Index: SPX) rose almost 6.3% during the second quarter of 2025. Standard and Poor reports the index ended 2025-Q2with a market cap of $52.50 trillion, a net gain of $3.09 trillion from the $49.41 trillion recorded at the end of 2025-Q1.

A little under four-fifths of the increase in market cap was concentrated within the top 10 stocks of the index, whose membership was unchanged from the end of the preceding quarter. The remaining 493 stocks that make up the market capitalization-weighted index contributed a little over one-fifth of the overall increase in the S&P 500′s total valuation. Together, these 493 stocks collectively increased in value by almost $444 billion.

But the S&P 500′s top 10 stocks increased in value by $2.649 trillion over the preceding quarter. Their disproportionate gain resulted in their share of the index increasing from 33.6% of its total value to 36.6%. Their share of the index is not as concentrated as it was at the end of 2024, but at $19.23 trillion, their combined value still represents an unusually large portion of the total market capitalization of the index.

The following chart shows the relative shares of the top 10 stocks in the S&P 500 at the end of the second quarter of 2025.

Here are the approximate market capitalizations of each of the S&P 500′s top ten component firms at the end trading on 30 June 2025:

• Nvidia (NASDAQ: NVDA) $3,852,990,130,563 (7.34%)
• Microsoft (NASDAQ: MSFT) $3,697,021,711,167 (7.04%)
• Apple (NASDAQ: AAPL) $3,064,383,420,526 (5.84%)
• Amazon (NASDAQ: AMZN) $2,072,918,104,171 (3.95%)
• Meta Platforms (A) (NASDAQ: META) $1,602,502,627,375 (3.05%)
• Broadcom (NASDAQ: AVGO) $1,296,092,241,895 (2.47%)
• Alphabet (A) (NASDAQ: GOOGL) $1,025,658,600,035 (1.95%)
• Berkshire Hathaway (B) (NYSE: BRK.B) $890,773,329,538 (1.70%)
• Tesla (NASDAQ: TSLA) $890,156,928,206 (1.70%)
• Alphabet (C) (NASDAQ: GOOG) $832,799,928,629 (1.59%)

While the membership list of the Top 10 stocks within the S&P 500 didn’t change from the end of the preceding quarter, their ranks within the Top 10 did undergo some substantial changes.

For example, Apple went from being the biggest publicly-traded company in the world, accounting for 7.01% of the total value of the S&P 500 to now be the third largest, with its share of the S&P 500′s value dropping to 5.84%. As it fell, it effectively changed places with Nvidia in the ranking of the S&P 500′s top 10 companies whose value soared during the final weeks of 2025-Q2. Since the end of 2025-Q2, Nvidia went on to become the world’s first $4 trillion company.

Meanwhile, the second largest company in the world, Microsoft, held onto its second place position, although its market cap rose from representing 5.87% of the S&P 500′s value to 7.04% of it.

The fourth and fifth-largest firms of the S&P 500, Amazon and Meta Platforms, also held onto their relative rankings, while their respective shares of the total valuation of the index increased. Amazon increased from a share of 3.77% to 3.95% of the S&P 500, while Meta Platforms’ share of the S&P 500 grew from 2.65% to 3.05%.

There is a new six-largest company in the S&P 500. Shares of Broadcom increased in value from 1.65% of the index to 2.47%, allowing the company to displace the Class A shares of Alphabet (better known as Google) and Berkshire Hathaway, which dropped from #6 to #8 in the mid-2025 ranking. Aside from Apple, Berkshire Hathaway was the only member of the S&P 500′s top 10 stocks to fall in value during the quarter, which saw its legendary CEO Warren Buffet finally retire.

Closing out the top 10, Tesla surpassed the Class C shares of Alphabet to claim the #9 slot in the Top 10. Alphabet’s Class C shares saw the smallest change among the S&P 500′s top 10 stocks, which was enough for the “other shares of Google” to still be included on the list.

Three months ago, the AI-bubble of the preceding two years had all but deflated, but with Nvidia’s surge during 2025-Q2, it would seem to be back with a vengeance. The rapid development of Artificial Intelligence technologies and its impact on the U.S. stock market is still among the biggest stories ever in market history.

References

Standard and Poor. S&P Market Attributes. [Excel Spreadsheet]. 30 June 2025. Accessed 1 July 2025.