Takayama and Judge introduced the price endogenous mathematical programming model as an alternative to the traditional econometric approach to sector-level policy analysis. McCarl and Spreen provided a review of price endogenous mathematical programming models. In that paper, they showed how price endogeneity can be introduced into a standard firm-level linear programming model. The introduction of price endogeneity allows expansion of the firm-level specification to a market-level analysis. At the time of publication of McCarl and Spreen, however, the application of price endogenous mathematical programming models was limited by the availability of software packages that could directly solve such models. The typical application used linear supply and/or demand relationships, which resulted in a quadratic programming (QP) specification. The advent of MINOS in the 1980s and then its incorporation into GAMS has lifted the computation constraint. In the present day, numerous price endogenous models have been developed. I can lay claim to six such models.