The top 10 largest companies in the S&P 500 now account for roughly 40% of the index's total value, the highest concentration since the mid-1960s, according to data from S&P Dow Jones Indices. This surpasses even the dot-com bubble peak of about 27%, with most of the largest stocks being tech companies heavily invested in AI, including Nvidia, Apple, Alphabet, Microsoft, Amazon, Broadcom, Meta Platforms, Tesla, Micron Technology, and Berkshire Hathaway. While this concentration has helped lift the market to record highs, it also poses a risk if tech stocks decline, especially if the Federal Reserve raises interest rates and slows AI infrastructure spending. History shows that only around half of the top 10 companies from 1965 remain in the S&P 500 today, collectively representing just 2.41% of the index's value. Investors are advised to build well-diversified portfolios with at least 50 stocks across all sectors and hold for at least five years to mitigate risk.
Apple Inc.
Amazon.com Inc
Broadcom Inc
Alphabet Inc Class C
Microsoft Corporation
NVIDIA Corporation
Berkshire Hathaway Inc
Meta Platforms Inc.
Micron Technology Inc
Tesla Inc