-18.02% is the change from 111 to 91
Calculation steps:
[( 91 - 111 ) ÷ 111] x 100 = -18.02%
Formula
Percentage change = [(91 - 111) / 111] x 100
Subtract the new number by the original number
91 - 111 = -20
-20 ÷ 111 = -0.18018018018018017
-0.18018018018018017 x 100 = -18.02%