General Discussion

S&P 500:

https://en.wikipedia.org/wiki/S%26P_500

The S&P 500 index is a public float weighted/capitalization-weighted index. The ten largest companies on the S&P 500 index account for approximately 38% of the market capitalization of the index and the 50 largest components account for 60% of the index. As of January 2026, the 10 largest components are, in order of highest to lowest weighting: Nvidia (7.17%), Alphabet (6.39%, including both class A & C shares), Apple (5.86%), Microsoft (5.33%), Amazon (3.98%), Broadcom (2.51%), Meta Platforms (2.49%), Tesla (2.31%), Berkshire Hathaway (1.68%), and Lilly (Eli) (1.55%).[4]
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NASDAQ:

https://en.wikipedia.org/wiki/Nasdaq_Composite

The NASDAQ Composite (ticker symbol ^IXIC)[2] is a stock market index that includes almost all stocks listed on the Nasdaq stock exchange... The composition of the NASDAQ Composite is heavily weighted towards companies in the information technology sector.
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Dow Jones Industrial Average:

Currently includes 6 IT companies (Apple, Cisco, IBM, Microsoft, NVIDIA, Salesforce) as well as Amazon.

https://en.wikipedia.org/wiki/Dow_Jones_Industrial_Average