Markets have spent much of the artificial intelligence boom debating whether valuations are too high and whether the extraordinary level of capital expenditure can ultimately generate an acceptable return. Those questions remain important. The more immediate development is that AI is becoming large enough to affect the macroeconomy itself.

The buildout is now interacting with electricity prices, corporate bond issuance, memory costs, industrial investment, labour markets and global interest rates. Governments are simultaneously borrowing heavily to financ...