Do you want a statistical percentage, or are you just gathering information out of which you will create the statistics?
I frequently listen to music while doing desk work. I find it helps me concentrate, relax, and focus. I couldn't tell you whether I am therefore more efficient, but I could guess so. I couldn't tell you the percentage!
I am a music teacher, so am making music all day every day, and often play music to teach the children about the masterworks or music of the world's traditions, also to teach them to listen! Never as background music, though I use some music (mostly instrumental) in that way at home.