A Proportional Symbols Map displays the cost index for each U.S. state, with larger circles indicating higher costs and the top ten states highlighted in red. The visualization uses a Mercator projection via `d3.geoMercator` and `d3.geoPath` to render state boundaries from a GeoJSON file. Circle radii are scaled from CSV data, and `d3.scaleThreshold` with `d3.schemeBlues` provides color encoding. The map is drawn in SVG with D3 v6, using `join()` to bind data points to circle elements and tooltips showing state names and cost values.