-81.33% is the change from 166 to 31
Calculation steps:
[( 31 - 166 ) ÷ 166] x 100 = -81.33%
Formula
Percentage change = [(31 - 166) / 166] x 100
Subtract the new number by the original number
31 - 166 = -135
-135 ÷ 166 = -0.8132530120481928
-0.8132530120481928 x 100 = -81.33%