European Central Bank analyzes US equity market resilience amid AI boom

Manu: A. Manu is an ECB economist and co-author of research on US equity market resilience during periods of strong earnings and shifting risk premia. The analysis contributes to understanding how AI-related developments have supported valuations. It is cited in the bulletin to explain decomposition of equity returns. Tomov: T. Tomov is an ECB economist and co-author of research analyzing factors behind US equity price resilience, such as earnings and risk premia. The joint 2024 work with Grothe and Manu informs the bulletin's discussion of market dynamics. It helps contextualize the role of AI-driven profitability expectations. Viola: M. Viola is an ECB economist and co-author of the 2026 ECB Blog examining the AI boom. The post provides context on technology-driven equity cycles. It is cited for insights into potential sustainability challenges. Grothe: M. Grothe is an ECB economist and lead author of research examining drivers of US equity price resilience, including earnings expectations and risk premia. The 2024 paper co-authored with Manu and Tomov is directly referenced in the current bulletin for its analysis of market structure and valuation factors. This work provides foundational context for the AI boom's impact on risk asset prices. Mendes: B. Mendes is an ECB economist and co-author of analysis on US market reactions to geopolitical shocks. The 2026 research contributes to understanding equity resilience. It is cited alongside related ECB work in the bulletin. ChatGPT: ChatGPT is an advanced AI language model developed by OpenAI. Its public release in November 2022 initiated the widespread AI boom that has driven innovation, investment, and equity valuation increases across multiple economic sectors. The bulletin identifies this milestone as the starting point for the earnings expectations and risk appetite fueling recent US market resilience. Nikolov: K. Nikolov is an ECB economist and co-author of the August 2026 ECB Blog post on the AI boom. The analysis addresses rational versus speculative elements in valuations. It supports the bulletin's forward-looking assessment of market concentration. S&P 500: The S&P 500 is a major US stock market index that tracks the performance of 500 large-cap companies. It serves as a primary benchmark for overall US equity market health and investor sentiment. The news uses S&P 500 data and firm-level distributions to demonstrate strong earnings growth, compressed risk premia, and rising concentration risks amid the AI boom. Corradin: S. Corradin is an ECB economist and co-author of analysis on the AI boom's implications for equity markets. The 2026 work examines potential boom-bust cycles. It is referenced to frame risks in a concentrated market environment. Andersson: M. Andersson is an ECB economist and co-author of the August 2026 ECB Blog post assessing whether the AI boom represents rational enthusiasm or potential bubble risks. The analysis provides broader context on technology-driven market cycles. It is cited in the bulletin for historical perspective on valuation trends. Vidaházy: V. Vidaházy is an ECB economist and co-author of research examining US equity market sensitivity to geopolitical risks. The 2026 analysis is referenced to highlight differential sector reactions. It supports conclusions on AI-related insulation from shocks. Breckenfelder: J. Breckenfelder is an ECB economist and co-author of the 2026 ECB Blog on the AI boom and associated market dynamics. The post explores enthusiasm versus sustainability concerns. It enriches the bulletin's discussion of profit expectations and investment sustainability. Ferrari Minesso: M. Ferrari Minesso is an ECB economist and co-author of studies on how US financial markets respond to geopolitical shocks affecting oil supply. The 2026 paper is referenced for insights into equity reactions during risk-off events. It supports the bulletin's findings on market insulation since the AI boom. Stalla-Bourdillon: A. Stalla-Bourdillon is an ECB economist and co-author of work on US financial market responses to oil supply shocks and geopolitical events. The 2026 paper aids in assessing equity market behavior. It informs the bulletin's event study on Middle East conflict impacts. Market Resilience: US equity markets have demonstrated unusual insulation from adverse macro and geopolitical shocks since the AI boom began in late 2022, with AI-related segments showing particular stability. Concentration Risks: High market concentration, especially in technology and AI-linked firms, raises the potential for spillovers from underperformance in a few mega-cap stocks to the broader equity market. AI Innovation Driver: The AI boom, sparked by ChatGPT's release, has spurred investment opportunities and productivity expectations across multiple sectors, underpinning equity valuations.