The boss of Norway’s $2 trillion sovereign oil fund has fired a warning to investors who have won big on the AI stock market boom, as he cautioned that “we are heading for a period of low returns.”

Nicolai Tangen, the CEO of Norges Bank Investment Management, said there was a new reality in the stock market amid geopolitical tensions and falling liquidity.

“The time of very low interest rates is gone. The world is a much more dangerous place,” Tangen told the Financial Times’ Unhedged podcast.

The companies that have solidified their place at the top of that new reality is becoming a risk in itself. Businesses that create or design AI semiconductor chips and those that use the tech for their burgeoning AI capabilities saw massive share price appreciation in the last couple of years.

Tangen said leadership in the stock market was very narrow, pointing out that the top of the market was now comprised of “companies with some kind of AI connection,” while the top 10 companies in the US S&P 500 (^SPX) accounted for around 20% of the index.

“The concentration is absolutely worrying. It means that there is a risk in the stock market which we have never seen before.”

Tangen described how the biggest players in the stock market were now heavily interlinked around the business of microchips. He cited Dutch giant ASML, “which makes the machines to make the chips,” before selling them to Taiwan. Many chips are then designed by NVIDIA (NVDA), before being sold to the likes of Amazon (AMZN), Meta, (META) and Microsoft (MSFT).

“So there are very few companies tied into them and they are getting bigger and bigger and more and more important.”

Norway’s tech risk

Despite his warnings about concentration risk in the stock market, Tangen’s $2 trillion oil fund is heavily invested in the companies he cited as key risk areas.

Norges holds more than a 1% stake in the U.S.’s biggest tech groups, including Microsoft, Apple, NVIDIA, and Alphabet. It also holds a sizeable stake in Taiwan Semiconductor Manufacturing Company (TSM).

Collectively, Norges owns $196 billion worth of shares in Microsoft, Apple, NVIDIA, Alphabet,, Amazon, Meta, TSMC, and ASML.

Tangen said heavy AI regulation in Europe meant it was likely that the big tech players would continue to come from the U.S.

“We have hardly any large tech companies in Europe, we are far behind. Will we manage to catch up? I would be surprised if we did.

“In America, you have lots of AI and little regulation, and in Europe, you have little AI and lots of regulation.”

This story was originally featured on Fortune.com