Stock Bull Market Turns Four; AI Spending Sustains Rally but Yields Pose Risk

What’s happening

The current bull market reaches its fourth anniversary next week, driven primarily by artificial intelligence spending and mega-cap tech dominance. Historical data shows bull markets that survive past their fourth year typically continue, but rising bond yields and energy price volatility present emerging headwinds to the rally's momentum.

Market impact

The longevity of this bull market has concentrated gains in a narrow set of AI-beneficiary stocks, creating valuation risks if sentiment shifts. Higher yields make growth stocks less attractive relative to fixed income, potentially triggering a rotation out of tech if the yield environment persists.

Broader implications

Four-year bull markets are relatively rare and durable, but this one's reliance on a single narrative—AI spending—leaves it vulnerable to disappointment in earnings or capital allocation. Macro headwinds including geopolitical risk and fiscal uncertainty could test whether this rally has further runway.