The S&P 500 is top-heavy with tech

 The S&P 500 SPX is up more than 7% so far in 2023, after last year’s 19.4% slide. 

The top 10 stocks hold a 29% weight in the index, and are responsible for around 70% of year-to-date performance

Concentrated leadership is far from unusual. In fact, it’s hard to avoid in an index that’s weighted according to market capitalization 

MarketWatch 12 May 2023

https://www.marketwatch.com/story/the-s-p-500-is-top-heavy-with-tech-heres-what-that-says-about-future-stock-market-returns-5b7b2e47

 It is important to remember the difference between capitalization-weighted indices such as the S&P 500 Index (SPX) and price-weighted indices like the Dow Jones Industrial Average (DJIA). 

While a cap-weighted index derives its performance from the movement of the underlying holdings multiplied by their respective allocations as determined by market cap, 

the Dow Jones Industrial Average is a price-weighted index, which simply means that stocks with the highest share price receive the greatest weighting in the index.

https://www.nasdaq.com/articles/understanding-the-djia%3A-how-price-weighted-index-performance-attributions-differ-from-cap#:~:text=While%20a%20cap-weighted%20index%20derives%20its%20performance%20from,price%20receive%20the%20greatest%20weighting%20in%20the%20index.