Start with the geography your firm actually serves
New Cassel is recorded by the U.S. Census Bureau as a CDP in Nassau County. That exact relationship should remain visible when you review attribution. A New Cassel landing page, a Nassau County page and a broader New York page are not interchangeable records, even when one firm serves all three areas. Attribution can help you inspect the landing page and channel associated with an inquiry; it cannot turn the population estimate into proof of demand or predict how many people will contact you.
Recommended approach
Define the geographic labels your firm already uses in intake and reporting. Review whether New Cassel, Nassau County and other service areas should be separate reporting views, then decide which landing-page and referral details are necessary to distinguish them. Keep the geography attached to observed journeys rather than using population as a forecast.
