The percent of change will always be represented by a positive number because that change is an absolute value. Absolute values will always stay positive because the direction is ignored. It's not like a -1 or a -2, but it's a zero or a 3. Hope this helped you out! :D
It’s biased because he is asking people who left a country concert and usually people who go to concerts go because it’s the type of music that they like, so the chances of someone saying they like a different kind of music probably won’t happen.