Dear All,
thank you for your responses. Austin's solution to remove rho helped a
lot, but I am a bit confused with the other alternative that he
proposed, namely "keep the rho, but divide by N". What would N be in
the case, where the mean of X is be computed on one domain, and mean
of Y on another? (e.g. because of the missings). For example, X is
income, and Y is family size, and I were interested in per capita
income, but income was less often reported than family size. My
observation is that Stata stops with error "no observations" in case
when domains of X and Y do not overlap at all, but there is nothing in
the formula that prevents me from computing (approx) moments of X/Y in
this case. Should I restrict computations to the common domain where
both X and Y are not missing for some reason?
Alan, thank you for the comments regarding not existance of moments in
case the the X and Y are N(0,s2). In my case the expectations of X and
Y are guaranteed to be non-zero as they are the numbers of people with
non-exotic characteristics (like attending primary school).
