If not everyone in your targeted geographic area is a good prospect for you, then applying some demographic selection criteria can be worthwhile. Demographic or Consumer mailing lists are based on public records, credit bureau, mortgage data, purchasing patterns, and survey results. If you are marketing for a school or a daycare, then you can choose to mail only to residents that have children a certain age or gender.
If you are selling high-end vacation packages, then you may only want to target residents above a certain income level. A roofing company would not want to mail to homes that were only recently built. A Demographic mailing list is a good fit for these and similar scenarios. If this sounds interesting, then start with a FREE mailing list count.