Nielsen bought out Elder and his partner, Louis Woodruff, and six years later he had developed a working prototype of his own "black box"; once installed in the home of a family (who were paid for their trouble), it would measure exactly what they were tuning in to. One by one, Nielson sent out his black boxes (which came to be called "people meters"), each one like a nerve ending into the body public, slowly creating a vast network that would tell him just how Americans were spending their evening hours. Thus were modern ratings born, becoming in the words of one expert "a feedback mechanism to the industry the same way that the human nervous system is to the human body." If the United States would now have a nervous system collecting information on the apportionment of attention, Nielsen would be its brain.

Tim Wu, The Attention Merchants, loc. 365