I work down the hall from one of the census district offices. I'm pretty sure they have a staff of at least 5 to 10, with untold numbers of other workers trained to go door to door later in the year to conduct the survey in person.
Multiply that out to every district in the country, add the federal administrators coordinating the whole shebang...
Eh, screw the math. We ALL work for the census. Please, won't you become... one of us? 0.0