That depends on the index.Equity indexes use a company’s market capitalisation to decide how much weight its shares will have in the index.
The S&P500 Equal Weight Index invests 0.2% in the top 500 companies in the US. The top 10 stocks make up 2% of the index.By definition, an index cannot be overweight any particular company or sector.
Is that more or less diversified than the regular S&P500 where the top 10 stocks make up 35% of the index?