A choropleth map colors countries by economic classification, with an interactive legend that filters the map to highlight a selected income group while dimming others. The visualization also includes a linked scatterplot showing GDP over time for each country, where points corresponding to the selected economic group remain opaque. Built with D3 v5, the map uses `d3.geoPath` and TopoJSON to render geographic features, while the legend and scatterplot are implemented as reusable functions. Data is loaded from a CSV file hosted on VizHub, and SVG is used for all rendering.