Callan and Thomas (1992) estimated a long-run translog cost function for the household goods sector of the motor carrier industry. The dependent variable was total long-run costs and the independent variables included were: The quantity of ton-miles produced The average length of haul, in miles The average load, in tons The percentage of household goods shipped, defined as a percentage of the total operating revenues generated by the shipment of personal effects and household goods The input prices for labor, fuel, capital, and materials