The Economic Law of Market Areas, so named by Fetter, is concerned wit
h the division of a territory between two competing centers. It is arg
ued that this Law can be conveniently examined in terms of six cases,
each of which is specified by a combination of differentials in freigh
t rates and prices at the two centers. The locational significance of
each case is considered, along with the form and dimensions of the mar
ket-area boundary between the two centers. Three of the cases are each
shown to subsume a special case. It is further shown that for any cas
e except one, a reversal of the differentials between the two centers,
while resulting in a symmetrically-equivalent outcome, requires a dif
ferent (and usually substantial) respecification of the case.