“…where M i is imports of the good concerned from i, i = 1,..., n; M is total imports of the good where M = *M i ; P i , i = 1,..., n, are import prices, P m is an index of import prices; P d is an index of domestic prices; and u v , v = 1, 2, are vectors of other variables. Equation (1), as shown by Leamer and Stern (1970) and pointed out by Testas (1996Testas ( , 1997, draws on the theory of demand where the quantity demanded for the good concerned is expressed as a function of its price and the prices of all other goods, in addition to income. However, as Winters (1984bWinters ( , 1985 has demonstrated, the necessary and sufficient condition for equation (2) to represent the allocation of imports adequately is that the process underlying the allocation be weakly separable between home and imported goods.…”