This example transforms U.S. Census County Business Patterns data for New York State, identifying the economic sector with the most establishments in each county. The visualization fetches county-level records via the Census API, filters out the “Total for all sectors” row, and uses `flatGroup` and `maxIndex` to summarize the dominant sector per county. The resulting JSON summary is displayed as text in a `pre` element, with all data processing handled through D3 v7 utilities like `csvParse`, `rollup`, and `bin`.