This visualization combines a U.S. state boundary map with red, green, and blue proportional circles to depict cost-of-living indices across states. Circle sizes scale linearly with each state's cost index using `d3.scaleLinear`, while positions are projected with `d3.geoAlbersUsa` and `d3.geoPath`. Data from `expstates.csv` is rendered in an SVG, and the ten highest-cost states are highlighted in green via a tooltip showing state names and indices.