The rise of artificial intelligence has pushed valuations across much of the US tech sector to levels that recall the dot-com era. Five economists tied to the European Central Bank (ECB) argue that a correction in current stock market valuations is likely even if AI lives up to the huge expectations placed on it. The warning matters especially for Europe: eurozone households have around €440 billion of exposure to US technology companies.
The AI stock market boom in 20 seconds
- US market valuations are near all-time highs by the CAPE ratio.
- The authors see a correction as probable, even if AI growth justifies today’s optimism.
- Nvidia captures the boom: its stock has risen about 20-fold since 2022.
- Eurozone households have roughly €440 billion exposed to US tech companies.
- Valuations in Europe are lower, but it would be hard to stay insulated from a US downturn.
The analysis, published on August 17, 2026, on the ECB blog, is written by Malin Andersson, Johannes Breckenfelder, Stefano Corradin, Kalin Nikolov, and Maria Antonietta Viola. One caveat: their views don’t necessarily represent the official position of the ECB or the Eurosystem.
Their question is a pointed one for the tech sector. AI could become one of the most important technologies of the coming decades and, at the same time, set off a market correction among the companies leading its development.
Those two outcomes aren’t mutually exclusive.
Nvidia shows how high AI expectations have climbed
Artificial intelligence has reshaped the tech industry in just a few years. GPUs, HBM memory, data centers, high-speed networks, and electrical capacity have turned into strategic resources as the big cloud providers pour more capital into infrastructure.
Nvidia captures that shift better than any other company.
The economists note that its stock has multiplied roughly 20 times since 2022, in step with the commercial explosion of generative AI and rising demand for accelerators to train and run models.
The question isn’t whether Nvidia is really selling more chips or whether AI is creating demand. Both are visible. The financial worry is how much future growth is already priced into the stock.
For that, they use the CAPE ratio, which compares the stock price to an average of ten years of inflation-adjusted real earnings.
The indicator for the US market sits near its all-time highs, close to levels seen during the dot-com bubble. In Europe it has risen too, but stays well below.
Comparisons to internet-era valuations call for caution. High valuations in two periods don’t have to end the same way.
In fact, the analysis points to something more interesting: you don’t even need a bubble for a correction to happen.
AI can meet expectations and stocks can still fall
Big technological revolutions often have a complicated relationship with financial markets.
The railway in the 19th century, electricity and radio in the early 20th, and the internet in the 1990s all created enormous growth expectations. These were real technologies that eventually reshaped the economy.
That didn’t stop cycles of sharp rises followed by falls.
The economists offer two explanations.
The first is grounded in rational markets. When a new technology appears, its economic impact is extremely hard to estimate at first. Early investors are buying, in a sense, a call option on a potentially huge future.
One company may fail, but another could become the next tech giant. That possibility justifies high valuations.
Things change once the technology spreads across the whole economy.
Uncertainty no longer sits in a few firms; it becomes a broader risk. Investors may then demand a higher risk premium and pay less for future profits.
Stock prices could fall even as profits keep rising.
The second explanation fits the traditional idea of a bubble: investors may overestimate a technology’s potential and push stocks higher than actual business results justify.
In both cases, a correction is possible.
That’s why the authors don’t label the AI market as rational or irrational. They think past technological revolutions make it reasonable to prepare for a correction at some point, even if they can’t say exactly when.
The Magnificent Seven hold much of the risk
AI development isn’t spread evenly across tech companies.
A large share of capital is concentrated in the so-called Magnificent Seven: Alphabet, Amazon, Apple, Meta, Microsoft, Nvidia, and Tesla.
Several of them hold key positions in AI infrastructure.
Microsoft, Alphabet, and Amazon run some of the largest cloud platforms in the world and are investing heavily in data centers. Meta is building its own models and large training infrastructure. Nvidia supplies much of the accelerators these companies use.
That concentration shows up in stock indices too.
When investors buy certain global funds or index ETFs, a sizable part of their money ends up invested, indirectly, in these giants because of their large market caps.
And that creates a link to Europe.
Europe has €440 billion exposed to US tech stocks
According to the analysis, eurozone households have roughly €440 billion of exposure to US tech stocks.
Much of it isn’t through direct purchases.
Investment funds are the main direct owners of Magnificent Seven shares among the European investors studied. Look through those fund holdings, and households show up as the largest group with indirect exposure.
Insurers and pension funds also hold relevant positions.
The rise of cheap ETFs and index-tracking products has let millions of investors tap US tech growth. At the same time, the sheer size of a few companies can create a concentration that isn’t always obvious to someone buying a global or diversified product.
A decline in these firms would reach beyond individual losses.
If a correction triggers large redemptions, funds may be forced to sell assets to cover withdrawals. Those sales could push prices down and prompt more redemptions.
The authors judge that a severe drop in the Magnificent Seven could pose a financial stability risk for the eurozone.
Europe is less caught up in the AI stock frenzy
The European tech sector is in a different spot.
Valuations in the eurozone have risen but stay well below US levels. European markets are still dominated by traditional sectors.
The economists also no longer see behavior in the European ICT sector that resembles the dot-com bubble.
That doesn’t mean Europe is on the sidelines of AI.
Business adoption is growing, and digital investment over the past decade has risen more than three times faster than the eurozone’s GDP, based on the data used in the analysis.
Europe’s AI stock boom may be milder, but it’s no shield against Wall Street.
US and European markets have historically been highly correlated. A major correction in US tech stocks could spill into European markets, hitting confidence, financing conditions, and corporate hiring decisions.
The real risk may be everything built around AI
The ECB analysis also lands at a telling moment for the industry.
The AI race isn’t only about building better models. The big tech firms are constructing data centers, buying accelerators, contracting electrical capacity, and rolling out networks to support expected growth in computing demand.
The market valuations of these companies depend, among other things, on whether those investments generate enough future revenue and profit.
That will be one of the main tests for the current AI cycle.
A slowdown in growth wouldn’t necessarily mean the technology has failed. It might just mean profits take longer than expected to justify the investment.
The internet offers a useful analogy.
The dot-com bubble wiped out enormous amounts of stock market value, but the internet didn’t disappear. It became the infrastructure behind much of today’s digital economy.
AI could follow a similar, paradoxical path: the technology may prove even more important than expected, even as the companies tied to it go through a significant correction.
The five economists don’t know when a correction might start, or from what level. They also don’t claim current valuations are irrational.
Their warning is more uncomfortable for an industry used to arguing about whether there’s a bubble: the correction could happen regardless of the answer.
FAQs
Do ECB economists believe AI is a bubble?
Not necessarily. Their analysis weighs both the possibility that valuations are rational and that there’s excessive optimism. In both cases, they see a correction as likely at some point.
Why is Nvidia in the analysis?
The authors cite Nvidia as an example of how sharply expectations around AI have risen. They note that its stock has multiplied roughly 20 times since 2022.
How much European money is exposed to US tech companies?
Eurozone households hold about €440 billion of exposure, mainly through investment funds and ETFs.
Would a market correction mean AI has failed?
No. The analysis notes that earlier technological revolutions went through boom-and-bust cycles yet ended up transforming the economy.
Sources: Portal Financiero and European Central Bank