Population density × median age for the whole planet — every inhabited square kilometre, brightness by density, color by the median age of its residents. Click anywhere for that cell's exact WorldPop age pyramid.
Caveats. WorldPop models age structure from each country's most recent census, disaggregated by satellite-mapped settlement — density is genuinely ~1 km, but age structure is uniform within source admin units, so effective age resolution varies by country and jumps at some borders. We are replacing the worst offenders with exact national data country by country — twenty-plus so far, from Japan's ~210k census blocks and the USA's 242k block groups (both rendered at 250 m when zoomed) to China's 2,844 census counties, France's 34,927 communes, and Korea's 3,493 dong; every upgraded country's popup names its exact source. Resolution varies geographically by design — the best available data everywhere. Elsewhere, the color adds a measured within-district gradient: on the eight census countries we measured how median age falls with density inside a district (sparse cells run ~6 years older, dense cells ~2 years younger), and apply that curve — scaled by demographic similarity, zero for high-fertility countries — while preserving every district's true aggregate pyramid (which is what popups show). Some countries cannot be improved: India's last census was 2011, Nigeria's 2006. Median within a cell is interpolated inside 5-year bands; 80+ treated as 80–100.