Jefferies Backs AI Stock Rally as Earnings Growth Fuels 80% of S&P 500 Gains
Such market concentration raises concerns among some market participants. However, Jefferies presents compelling evidence supporting the rallys foundation. The firms quantitative analysts examined the underlying factors propelling these gains. Their conclusion: legitimate earnings expansion, not valuation inflation, fuels the advance. This differentiation proves critical for investors assessing bubble risk. The AI baskets forward earnings projections for 2026 have surged more than 30% since the middle of last year. Projections show compound annual earnings expansion of 38.5% for AI-focused companies spanning 2026 through 2027. Meanwhile, non-AI sectors project growth of merely 11.9%. Despite robust growth expectations, AI stocks trade around 25 times forward earnings. This multiple sits beneath the sectors one standard deviation threshold. The price-to-earnings-growth metric stands at just 0.6 times. “AI is the cheapest sector to own in the U.S.,” Jefferies strategists stated in their research report. Performance Varies Across AI Subsectors The AI sector shows considerable performance dispersion. AI server manufacturers, optical component suppliers, and memory producers have delivered superior returns this year. Cloud hyperscalers and chip architecture firms have underperformed. From a valuation perspective, memory and compute infrastructure appear most compelling on a PEG basis. Semiconductor equipment makers and chip designers carry higher relative valuations. First quarter 2026 earnings results provided additional insight. Approximately 86%