This D3.js proportional symbols map visualizes the cost of living index across US states. Gray states are drawn with the `d3.geoAlbersUsa` projection and `d3.geoPath`, while semi-transparent red circles, sized by a square-root scale, are placed at state coordinates derived from an external latitude/longitude source. A legend displays four bubble sizes with corresponding index values. Hovering over a circle reveals a tooltip with the state name and cost index. Data is loaded via `d3.json` and `d3.csv`.