but conceptually, simon gave it a degree of depth and, measurementwise, a degree of reality that never prevailed before. one of kuznets' basic concepts was to limit measurements to the marketplace. the amount people paid for goods and services measured consumption. the money spent on new production facilities and equipment gave a total for investments. the problem was to avoid double counting as payments flowed through the economic system. take an automobile. the iron mine operator gets income. the steel mill owner gets income. the manufacturer gets income. to avoid the inaccuracies of counting the same money three times, kuznets decided to use only final sales, in this case, the amount paid for the automobile at the dealer's. the value added along the way is found by deducting the cost of the finished steel from the amount paid for the car. not all the nation's work is performed on assembly lines. up to 1/4 of the work in the economy is at home. kuznets excluded cooking, cleaning, and child care provided by housewives because it was too hard to measure and because of the kind of work