My book club is reading *Abundance* by Ezra Klein and Derek Thompson. The core idea fits on a napkin: housing, clean energy, cures for disease haven’t changed inputs, but the pipe between inputs and output has clogged with valves—each a reasonable checkpoint added over decades. Klein and Thompson call this chosen scarcity, akin to unaddressed technical debt in legacy code.

I tested the claim with real data. Austin, which began clearing valves around 2015, permits about 18 new homes per 1,000 residents yearly, while San Francisco permits only 2—an eight times difference in throughput. Using an elasticity from an Auckland policy study, the model predicted Austin’s price effect would blow past –100 %, showing market saturation, and forecast an 11 to 19 percent rent decline for SF. Instead, SF rents rose nearly 19 % over the past year, swamped by an AI hiring boom that a supply‑only model missed.

A second test compared Vienna and London, which build housing at nearly the same rate (within 2 %). Yet Vienna’s rent is about a third of London’s and has stayed flat for two decades. The reason: 43 % of Vienna’s stock is public or nonprofit housing, operating alongside the private market, plus old rent‑control rules. Vienna built a second pipe; London kept adding valves to the old one. The takeaway: clearing the pipe works when isolated, but other levers—parallel systems and regulation—also shape affordability. Before accepting a big claim, profile first; don’t assume you know the bottleneck.