@sapphire @sickburnbro @CleverMoniker Back in the day, it was Arbitron. If you were selected to participate, you were supposed to keep a diary of what you listened to. It was seriously that grug-tech. There wasn't a lot of accusations of chicanery and fuckery, but there was some.

Everybody kinda sorta knew it was pretty limp data, but a lot of station managers lived and died by it. The college radio stations all ignored it, and that's why you got a bunch of folks who knew about The Smiths and REM and whatnot back in the day. The college stations also tended to be low-power, so they operated under somewhat different rules, IIRC.