Eventually the Chinese government, despite all its tanks and brutality and nuclear weapons and gulags, must bow before Stein’s Law: “If something cannot go on forever, it will stop.”

China’s current economic reversal is being driven in part by a slowdown in construction. As it turns out, if you build enough ghost cities full of empty apartment blocks, then the oversupply in the market eventually makes it unprofitable to build more empty apartment blocks. (Counterintuitive, right?) Students of Austrian economics will recognize this as the old problem of “malinvestment,” capital’s being misallocated because of subsidies and other distortions. Who’d they build those apartment towers for? Who cares? If there’s free money on the table, somebody is going to pick it up.

The ripple effect that provided Beijing’s rationale for all these subsidies is reversing itself: Construction supplies had been an important contributor to the Chinese domestic economy, but now cement production is falling, glass production is falling, and steel production is falling faster than it ever has. If you happen to need a few million tons of steel, China is having a fire sale on the stuff, which of course enrages American politicians, because what good could possibly come of lower prices for enterprising Americans who want to build things?