This proportional symbols map displays the cost index of US states using circles positioned by geographic coordinates, with the ten most expensive states highlighted in red. The visualization uses D3 v7 with `d3.geoAlbersUsa` projection and topojson to render state boundaries, while a `d3.scaleSqrt` size scale maps cost index values to circle radii. Hover interactions reveal tooltips, and a legend explains the symbol scaling. Data is loaded from CSV and US Atlas TopoJSON sources.