Some of the biggest US companies have had a great run over the last decade. The performance has been so good that some of the biggest companies outperformed the S&P 500 and rekindled concerns around market concentration. Is this recent occurrence unique to today or backed by history?
Henrik Bessembinder answered that questions with his latest research into “do nothing” portfolios. One of the things he looked at was the performance of concentrated portfolios in the largest S&P 500 stocks compared to the overall index.
Bessembinder broke down the largest stocks into four market cap-weighted portfolio buckets: the single largest stock, 10 largest stocks, 50 largest, and 100 largest. Each portfolio was rebalanced each year into its corresponding number of largest stocks starting in 1971. Returns where then calculated through 2025 and compared to a portfolio of all S&P 500 stocks.
The results are below.
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