Resolution

Every level below describes the same territory. What changes is how finely it is cut, and with it how much the map can say and how much of it is reliable. Coarse levels report everything and reveal almost nothing; fine levels resolve street-level difference and start withholding numbers because the samples behind them are too small.

Census tract, 2,324 tracts. The workhorse level: roughly 1,200–8,000 people, drawn to be demographically coherent. Most place-level research is tract-level.