Developed by Archibald Crossley, the ratings were generated using information collected by telephone surveys to random homes.
In 1930, Crossley spearheaded the formation of the Cooperative Analysis of Broadcasting (CAB).
[1] The first national ratings service, CAB was supported by subscription and was at first available only to advertisers.
[2][3] Crossley's method of data collection essentially consisted of calling random households in selected cities and asking the respondent to recall what radio programs had been listened to at an earlier point: the previous day in Crossley's first surveys,[4] later modified to a few hours earlier.
[2] The survey is alluded to during Orson Welles' opening narration for his famous 1938 radio dramatization of The War of the Worlds: "On this particular evening, October 30th, the Crossley service estimated that thirty-two million people were listening in on radios.