What US history tells us about AI capex | Idea Farm

What US history tells us about AI capex

UBS

Ulrike Hoffmann-Burchardi

Research

4 Pages

July 2026

Ulrike Hoffman-Burchardi looks back at three key lessons from America’s great historical capital cycles. She then applies them to the most important market question today: the trajectory of AI.

Key Takeaways

Capex Cycles Rhyme: Railroads peaked at 6% of U.S. GDP, while internet infrastructure reached roughly 4% in 2000.

Overbuild Is Common: After the 1990s telco boom, 95% of installed fiber sat dark and unused when demand lagged supply.

AI Still Scales: UBS estimates AI capex could reach 3% of U.S. GDP next year, driven by agentic and autonomous AI.

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