Previously know about. there might be people in the household that you didn't know about, a relative visiting that you weren't expecting. there will be stuff that people are expecting to find, but there will also be, for some people, there are always going to be some surprises. many of those who filled out the census were war veterans. they'd been promised homes for heroes, but millions returned to overcrowded slums. one householder wrote on his form, "stop talking, start building". his name was james bartley, he was a gas fitter, and he lived with his wife and three small children in one room...