Origin of POSSLQ

I looked up the etymology of this on etymonline, but it doesn't state the origin. It only defines what it stood for. It did tell what its date of origin is however, but that isn't what I was looking for.

Can someone please tell me its origin?

Wikipedia article:

POSSLQ ( /ˈpɒsəlkjuː/) is an abbreviation (or acronym) for "Persons of Opposite Sex Sharing Living Quarters," a term coined in the late 1970s by the United States Census Bureau as part of an effort to more accurately gauge the prevalence of cohabitation in American households.

And Dictionary Online seems to agree, at least about users of this acronym