Your product sells into a kind of site that has no register. Company databases give you the firm and often only its head office. The association list covers the members who joined, and the sales team knows their own patch.
So the addressable market gets sized from an estimate with a wide range, and territories and quotas are cut on it. A cluster of sites that was never on any list tends to turn up later, in the field. This sweep replaces the estimate with a list of candidate sites you can count, plot and check.
