Markets Are Not Pricing a Bubble. They Are Pricing an Earnings Revolution.

US equities are not necessarily in a valuation bubble because the market rally is being supported by an unusually strong earnings cycle, although the durability of AI-related investment is the key risk.

• The S&P 500 has reached record highs alongside corporate profits, while its price-to-earnings ratio has changed little; technology valuations have actually compressed as earnings grew faster than share prices.
• Consensus forecasts point to S&P 500 profit growth of roughly 30% in 2026, 13% in 2027 and 14% in 2028, implying cumulative earnings growth of approximately 67.5% over three years.
• If the index returned 10% annually through 2028, it would be about 33% higher, while earnings would be nearly 68% higher, making the market more than 20% cheaper on an earnings basis.
• The main driver is an AI investment cycle involving hyperscalers, semiconductor manufacturers, networking equipment, cloud services and enterprise software, with industry forecasts expecting peak spending only after several more years.
• The historical precedent of railways, telecom networks and the internet suggests that capital-expenditure booms eventually consolidate, creating a risk that hyperscalers shift from expansion to optimisation.

Takeaway: Investors should focus less on current valuation multiples than on the persistence and quality of earnings growth, with active stock selection becoming more important as the gap widens between companies converting AI spending into durable profits and those relying mainly on the narrative.