Signal Just over half of S&P 500 market-cap growth from 2021 to 2025 came from seven firms

Summary

MGI points to the concentration of recent US stock market gains in a small number of companies. Just over 50 percent of the rise in S&P 500 market capitalization from 2021 through 2025 came from the so-called Magnificent Seven, a group of firms commonly associated with AI. This concentration is part of the technology and AI boom behind US equity values standing close to double their historical average relative to GDP in 2025. The report names the growing share of corporate profits in GDP as a second driver behind the rise. Because so much value rests on a few AI-linked firms, the durability of their earnings becomes a key question for US equity valuations.