This choropleth map visualizes estimated population by country, with color encoding from light blue to dark blue based on population magnitude. It uses D3 v7's `geoMercator` projection and `geoPath` to render world country boundaries from TopoJSON data in World Atlas. Population values come from the accompanying TSV file, which maps ISO country codes to their `pop_est` estimates, and a `scaleLinear` determines the fill color per nation.