In its 2026 outlook report, the shop known for its index funds ran through various scenarios in which AI proves out and in which it disappoints. The bull case for AI is that it eventually boosts the U.S. economy: Vanguard sees GDP growth hitting 3% on average between 2028 and 2035. But what's good for the economy isn't necessarily good for stocks. Vanguard's expectations for the U.S. market stem largely from its risk-return assessment of large-cap shares, a useful reminder that theS&P 500's double-digit ret ...