When you find a person of interest in a census, do you look at all the contexts in which that person appears? There are not as many details in pre-1850 census records, but for enumerations after that date, do you look at how many of your ancestors neighbors are from the same state or country as he? Do you look and see how many homes in the neighborhood are rented, owned or mortgaged? How common is his occupation? How common is it for the wife to have an occupation outside of the home?
Not all census enumerations provide these details, but there are multiple layers of context that can be easy to overlook.