€440 Billion at Risk: ECB Experts Warn of an AI Bubble Burst

A group of economists at the European Central Bank has put a blunt warning on the table: if AI stocks correct, the euro area will feel it, and not just through a few direct shareowners. The team — Malin Andersson, Johannes Breckenfelder, Stefano Corradin, Kalin Nikolov and Maria Antonietta Viola — argues that the bigger European risk sits in household fund holdings, which many savers may not realise are packed with US tech exposure.

Their starting point is the level of market pricing. In the US, the S&P 500’s cyclically adjusted price-to-earnings ratio is now close to its historical peak, at a level last seen during the dot-com bubble. Europe’s valuations have also risen, though not as far. And the authors see two familiar ways these tech booms tend to end.

One is the sober version: new technology creates huge upside, but also huge uncertainty. That uncertainty can lift prices early on, as with Nvidia, whose share price has risen twentyfold since 2022. But once the technology spreads through the wider economy, the risk stops being a quirky bet inside one portfolio and becomes something broader and harder to diversify away. Investors then ask for a higher risk premium, and that has often mattered more than the extra cash AI may eventually generate.

The other explanation is less flattering. If enthusiasm runs ahead of fundamentals, prices can simply outrun reality, then snap back hard when sentiment changes. The ECB blog says nobody can predict the timing in advance. Boom-bust patterns are usually obvious only after the fact.

For Europe, the key point is exposure. The ECB estimates euro-area households hold around €440 billion in US technology stocks, mostly indirectly through investment funds and ETFs, based on look-through data for the third quarter of 2025. Insurers and pension funds also have sizable positions. That fund structure matters because redemptions force managers to sell assets, starting with the easiest ones and, under pressure, moving into harder-to-sell holdings too. That can drag prices down further and trigger more outflows.

The ECB’s economists do not think Europe is building its own homegrown AI bubble in the same way the US seems to be. European valuations are lower, ICT productivity and margins are improving, digital-services sentiment looks steady, and AI adoption has risen sharply only a few years after ChatGPT. But the region’s stock markets are tightly tied to Wall Street, and that is the real problem. A US correction would not stay neatly American; it would spill into European sentiment, financing conditions and hiring.