This example shows a pair of choropleth maps of the world using a linear blue-to-red color scale to encode each country's birth rate, with missing data rendered in grey. The maps are drawn side-by-side as two SVG elements, each using `d3.geoEqualEarth` projection and `d3.geoPath` to render GeoJSON features. Data comes from a CSV of world statistics loaded with `d3.csv`, and country geometries from a GeoJSON URL via `d3.json`. The code uses React and D3 v6, with a `Map` for lookups and `d3.scaleLinear` for color mapping.