Denominators: Eurostat is the obvious answer and it is wrong

Most SDG indicators are rates per 100,000, so every non-US city needs a population figure before it can produce a chart. Two are now wired, and the route we did not take is the more useful finding.

Eurostat's Urban Audit publishes greater cities

urb_cpop1 covers 969 European cities annually and is exactly the single source this needs. It reports greater cities, not municipalities:

For Madrid the table contains no municipality entry at all — the greater city is the only option. A city's open data covers its municipality, so this is the denominator mismatch the whole project exists to catch, and it would have been completely invisible in the output.

So denominators come from the cities themselves

Better provenance as well: numerator and denominator then share a publisher.

Madrid — Padrón municipal (200076-0-padron), summing the four Spanish/foreign × male/female columns of a 34 MB CSV: 3,520,396 as of 2026-09-01. A snapshot, so Madrid supports levels and not trends until the historic padrón is wired.

Milan — Popolazione calcolata (ds1494), year-end population 1880–2025, ISTAT to 2002 then the city's own anagrafe: 1,399,079 in 2025. A series, so Milan supports trends — the first non-US city that does.

Two cities, two shapes, two resolvers. City statistical publications do not share a format, and pretending otherwise is how you end up with Eurostat.

The bug this work exposed

Building a summary table showed Chicago and Boston both reporting 8,478,072 — New York's population.

The census resolver fell through to NYC's place code whenever a city declared none of its own. Chicago's registry entry named its place code in a prose source string but carried no structured field, so it silently inherited NYC's 8.5 million. Every Chicago rate would have been three times too low, and nothing in the output would have looked wrong.

There is now no fallback. A city using the census module without explicit state and place FIPS raises, with the reason: refusing to guess, a wrong denominator is invisible in the output.

That is the fifth automated path on this project that produced a confident wrong answer, and the second where the failure mode was a silent default rather than an error.

Where it stands

Plus 23 more US cities resolvable by ACS place code. Buenos Aires declares no source and is refused rather than estimated. 24 non-US cities still need one, and each needs a person to find its statistical publication — the part that does not automate.