This proportional symbols map overlays circles on a U.S. state map to visualize grocery cost indices, with the ten most expensive states highlighted in red and a legend showing cost values. The visualization uses D3 v3’s `d3.geo.path`, TopoJSON, and a queue to load map boundaries, state centroids, and cost data. Point radii are scaled with `d3.scale.sqrt`, and hovering a circle triggers a tooltip, dims other symbols, and uses an SVG transition for emphasis.