With the potential dollar value of television's attention harvest becoming so obvious, any pretenses to a higher purpose that broadcasting once had were eroding quickly. Now it was clear, as an economist put it, that “programs are scheduled interruptions of marketing bulletins.” The trend was exacerbated by another increased quantification. The networks began to consider audience attention their “inventory,” which was sold using metrics like “gross rating points” or GRP, a formula that estimated the likelihood of people seeing the advertising at least once (the cumulative audience), and the frequency with which the advertising played. On popular prime-time television, all but the highest commercial bidders—America's largest corporations—were priced out of each time slot.

Tim Wu, The Attention Merchants, loc. 489