A measure of the extent to which two countries export the same products. Defined for exporting countries j and k as XS_jk = _i(min(X_ij,X_ik)100), where X_ij,X_ik are the shares of product i in their total exports. XS_jk ranges from zero if they have no exports in common to 100 if they export the same things in the same proportions.