Some economists have applied multiple regression analysis to national aggregate time series data to measure elasticities of demand for all food marketing services. This paper demonstrates the inappropriateness of the measures of marketing services price, quantity and value used in the analyses. The services price index used was actually a services value index; the services quantity index used was an index of food quantity; and the measure of value used contained errors of observation of such a nature as to lead to biased elasticity estimates. Finally, formulas are suggested which might be used for the construction of a Laspeyre's index of services prices and a Paasche index of quantity of services.