This example pairs a choropleth map with a scatterplot to explore global demographic data. The map colors each country by birth rate using `d3.geoEqualEarth` and `d3.geoPath`, while the scatterplot plots fertility rate against life expectancy, with circle size encoding population and color indicating continent. Hovering over a country on the map highlights it in red; hovering over a scatterplot point also turns it red. The code loads GeoJSON map boundaries, a CSV of country statistics, and a JSON continent mapping, processing the data into a `Map` for lookup.