Instructions:

1. List the 20 artists you listened to the most.
2. Find out how many listeners they have on Last.FM
3. Add all the listeners together.
4. Divide by 20.
5. Divide this average by the number of Radiohead listeners on Last.FM (at the time of writing: 1,582,316).
6. Multiply by 100 to get a percentage.
7. Voilà, your mainstream-ness has been returned to you.

01.) The Strokes || 34,279,588 plays
02.) Tegan and Sara || 22,162,560 plays
03.) The Last Shadow Puppets || 2,833,913 plays
04.) Adam Green || 4,528,615 plays
05.) The Beatles || 125,960,136 plays

06.) Coldplay || 77,225,507 plays
07.) The Kills || 4,517,770 plays
08.) Albert Hammond, Jr. || 1,354,675 plays
09.) Kaiser Chiefs || 15,764,830 plays
10.) Amy Winehouse || 23,361,098 plays

11.) Hot Hot Heat || 9,489,497 plays
12.) The Fratellis || 9,976,931 plays
13.) The Cribs || 4,525,035 plays
14.) The Long Blondes || 2,441,118 plays
15.) The Pipettes || 4,166,661 plays

16.) The Pigeon Detectives || 3,119,223 plays
17.) The Kooks || 23,622,366 plays
18.) Arctic Monkeys || 49,589,377 plays
19.) Oasis || 35,116,051 plays
20.) M.I.A. || 10,361,259 plays

ok, so i'm not good with big numbers and i either got 1%, 14% or 148% and since 14% is the most reasonable answer i'll just settle for 14%, i guess.