The Nasdaq share index had its worst day in 18 months after slumping 5.5% on Thursday amid growing signs that the artificial intelligence industry will face tougher regulation because of the midterm election results.

As Wall Street sustained widespread losses, the Nasdaq composite tumbled into “correction territory” – more than 10% below its recent record high – with more than $2tn shaved off its value by the end of trading Thursday. The tech-heavy index had its biggest one-day fall since Donald Trump announced his “liberation day” tariffs on US trading partners in April 2025.

Worries over massive AI spending gripped the New York stock market and rippled out to other bourses worldwide as investors anticipated tougher scrutiny of datacentre expansion plans.