Income Inequality / Wealth Concentration Index (Gini Coefficient)

From the Housing and Land Survey's published municipal-level distribution of household income across 6 bands (under ¥3M / ¥3–5M / ¥5–7M / ¥7–10M / ¥10–15M / ¥15M+), we assume a representative value (midpoint) for each band, approximate a Lorenz curve, and estimate a Gini coefficient (0 = perfect equality to 1 = perfect inequality) along with the median income.

Gini coefficient = 1 − 2 × (the area under the Lorenz curve, approximated via the trapezoidal rule from each band's cumulative household share and cumulative income share)

*Official Gini coefficient calculations (e.g. the Ministry of Internal Affairs' Family Income and Expenditure Survey) use roughly 19 detailed income bands, whereas this index approximates from just 6 bands and is therefore comparatively coarse. In particular, the open-ended "¥15M+" band assumes a representative value (1.5× the ¥15M floor = ¥22.5M), which may understate actual inequality. Use as a reference only. No town/chome-level data exists — municipal level only.

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Other indicators

Sources: MLIT Real Estate Information Library (Real Estate Transaction Price Information), Statistics Bureau of Japan (Census), Tokyo Metropolitan Police Department (reported crimes by town), Saitama, Chiba and Kanagawa Prefectural Police (open crime data), Tokyo Metropolitan Government (Basic Resident Register population), National Land Numerical Information, and others (compiled and processed by topos labs). Individual transaction prices are processed at publication and may differ from actual prices.