A UN agency's communications team drafted a world choropleth shaded by total population. It shows China, India and the United States as the only dark countries and says nothing that a reader did not already know. The reviewing cartographer sent it back with one note — a choropleth shades a rate, never a count — and asked for the same map shaded by density. The countries layer has population and no area column.
Return every country as a polygon, carrying:
iso_a3, namearea_km2 — the polygon's area on the ellipsoid, km²pop_density — pop_est divided by area_km2, persons per km²Measure the area from the geometry in an equal-area projection or geodesically. A count map shades whoever has the most people; a density map shades where people are close together, which is the thing a reader cannot see on their own.
Return all countries, in EPSG:4326, densest first.
These are where the teaching is. Read them twice.
Shading a count instead of a rate is the first thing a map reviewer checks, and the reason most population choropleths in the wild are wrong.
6 scored, 0 informational
One feature per country
18%Carries iso_a3, name, pop_est, area_km2 and pop_density
18%World population across all countries
18%The densest unit's density
27%Result is polygons
9%Submitted in EPSG:4326
9%