# Communities of Interest A redistricting criterion directing mapmakers to keep together populations sharing common social, economic, cultural, or policy interests — neighborhoods, tribal lands, media markets, watersheds, industry regions. Roughly half the states name it as a criterion, and it is the **least defined** of the traditional criteria: there is no accepted metric for it, statutes rarely specify one, and reasonable mapmakers can invoke it to justify opposite lines. That makes it the criterion most often used to supply a neutral-sounding rationale for a line drawn for other reasons — and, conversely, the main channel through which public testimony enters the process at all.