Doug (or anyone),
Would it be correct to say that when economists say A varies directly as B (or some similar proposition) they usually do not have the slightest idea as to whether the correspondence is significant or utterly trivial??? Or if it is significant, it is unknown
whether A causes B or B causes A or C causes Q which causes both? Or is the whole thing usually a tautology built into the questions asked?
A professor of education at the university of michigan once made the astounding discovery that the rate at which children acquired new words while learning to read was the same as the rate at which telephone poles wore out. (Both followed a bell curve.)
Carrol