This choropleth maps U.S. county-level unemployment rates from 2008, encoding values from 0 to 15% using a quantize scale with nine discrete color classes. The SVG visualization uses a Mercator projection and TopoJSON data for county and state boundaries. Unemployment data is loaded from a TSV file and joined to county IDs via a `d3.map`, with each county’s fill class (q0-9 through q8-9) assigned by the quantized rate, producing a blue sequential palette from light to dark. County boundaries are stroked in white and state borders in white with rounded joins, while the background remains transparent. The example highlights the use of quantize scales for continuous-to-discrete mapping and suggests a threshold scale as an alternative for arbitrary ranges.