I stand corrected. My cursory google search didn't turn up anything concrete, so I fell back on some things I've heard but can't quite place the origin. My understanding was that wealthier families had, on average, ~2 children, but lower income families tended to have more than that. That, of course, does not necessarily mean that the average household size will be larger (there may be more or less unwed or divorced households at lower income levels).

Of course, my point still stands: just because it's 1% of households does not necessarily mean that it's >1% of people (it may very well be, though).