How Changing a Denominator Can Flip a Property Tax Map Without Altering the Data

A data analysis using Chilean government records demonstrates how property tax maps can produce contradictory conclusions depending on which denominator is chosen — households, residents, or land area — without any change to the underlying figures. The study cross-references Chile's national real-estate cadastre from the tax authority SII with the IGVUST, a socio-territorial vulnerability index published by the Ministry of Social Development. The unit of analysis is the Chilean neighbourhood unit, a civic territory not designed to cover the entire country, meaning rural areas are excluded by default — a gap that can silently distort results. The author argues that while the arithmetic involved is straightforward, the problem lies in presenting one type of territorial indicator as though it answers a different question. The core finding applies beyond Chile: any jurisdiction that maps property assessments against deprivation measures faces the same methodological choices, and mislabelling them produces misleading narratives.