The census is very accurate. If someone doesn't answer the door on the first visit, our workers will go back as many as six times on a different date and time. We'll leave them a note just letting them know who we are and why we're in the area. We also tell them that we'll be coming back. We leave them our name and number so they can call to verify.
They basically just learn how to take down information and stay in their own area. They also learn common-sense safety rules.