Adult contemporary music:

Adult contemporary traces its roots to the 1960s easy listening format, which adopted a 70-80% instrumental - 20-30% vocal mix. A few offered 90% instrumentals, and a handful were entirely instrumental. The easy listening format, as it was first known, was born of a desire by some radio stations in the late 1950s and early 1960s to continue playing current hit songs but distinguish themselves from being branded as "rock and roll" stations. Billboard first published the Easy Listening chart July 17, 1961, with 20 songs; the first number one was "Boll Weevil Song" by Brook Benton. The chart described itself as "not too far out in either direction".

Please answer a question about this article. If the question is unanswerable, say "unanswerable". Generally speaking, what percentage of music on easy listening stations was instrumental?
70-80%