I wrote: "Hence, if the labor theory of relative prices were true,
the regression coefficients would have to have the same "true"
values whichever equational form was specified and whatever Zj (not
equal to Xj or Yj) were chosen."
The restriction on Zj in parentheses should instead be "(for [Z] not
equal to k[X] or k[Y], where k is a constant and [.] indicates a
vector)".
Andrew Kliman