AI Firms Make Up 45% of S&P 500, Dominate U.S. Credit
AI-linked companies now represent 45% of the S&P 500 market cap and 15.4% of U.S. investment-grade debt; AI-related corporate debt totals $1.4 trillion.
Recent data show companies tied to artificial intelligence account for 45% of the S&P 500’s market capitalization and 15.4% of U.S. investment-grade debt. Outstanding corporate debt linked to AI activities stands at $1.4 trillion.
The share of S&P 500 market value held by AI-linked firms rose about 20 percentage points since November 2022, when ChatGPT was introduced.
On the credit side, AI’s portion of investment-grade debt has increased roughly 3.5 percentage points since 2020, making it the single largest segment of that market. Total AI-linked debt has nearly doubled from 2020 levels.
Large cloud and AI service providers — Amazon, Alphabet, Meta, Microsoft and Oracle — together issued about $121 billion in U.S. corporate bonds in 2025. That compares with an average of roughly $28 billion a year from those five firms between 2020 and 2024.
AI-linked equities rose in value, expanding their weight in benchmark indices and reducing the weight of other sectors. The concentration of market value among a small set of companies has changed index composition and investor flows.
Outside the United States, Taiwan’s total stock market capitalization climbed to about $4.14 trillion, exceeding the United Kingdom’s roughly $4.09 trillion for the first time. Taiwan’s market value has roughly tripled since 2020, led by semiconductor firms; Taiwan Semiconductor Manufacturing Company accounts for more than 40% of the country’s market capitalization.
A market newsletter wrote, “Never before has a single theme dominated both US equity and credit markets to this magnitude.”
Market data show that companies’ investments in AI infrastructure and services have been accompanied by rising equity valuations and increased corporate borrowing tied to those activities.
