This choropleth map visualizes global income groups, coloring each country according to its income_grp category with a spectral color scale. The map uses a natural Earth projection and supports zooming via the zoom API, while a legend explains the color categories. The visualization loads world country geometries from the world-atlas TopoJSON and TSV datasets, processes them with topojson.feature, and renders the paths using d3.geoPath. Hovering highlights a country in gray and reveals a tooltip with its name and income group.