I have an all-ASEC sample and I am trying to just count observations per year, of households and of people, and I am getting some results I don’t understand. The household numbers seem sensible – starting around 25 or 30 thousand in the sixties, gradually rising to about 100 thousand currently. with big jumps around '66, '76, and 2001.
But the number of observations of people is weird – nothing resembling a stable relationship between number of people and number of households. You see an enormous rise from about two people per household to in the early 60s to almost four in 1980, and then there is a very regular pattern of bouncing back and forth by almost a full person in alternate years, but with a slow overall decline until around 2017, when it suddenly jumps up by, like, two full people. These are unweighted observations, so I don’t expect them to accurately reflect the true population ratio, but still, why the alternate-year pattern and the sudden recent jump? I would assume that this is a programming error of mine, except that I calculated it two different ways, by just counting lines and by summing the maximum PERNUM in each household. Is there an alternate-year oversample or something?