There are 4 types of ZIP codes: Standard, unique, PO Box, and military. Standard type zip codes should return nearly complete information for each request. The others will have very limited data (if any) returned simply because they do not server a large area or demographic. 05255 returns a large data set for me. Can you let us know what you think is missing? 94026 is PO Box ZIP code so will not have much data in the response.