“…3 A relevant exception is represented by the ML approach to estimate simultaneously demand and supply equations in a disequilibrium model, where the observations belong, respectively, to a demand or to a supply function (see, among others, Maddala and Nelson, 1974). The choice of the regime does not depend on a third selection equation, but the likelihood function specified in this model, including coefficients and variances, does not include the across-regime covariance.…”