-81.87% is the change from 171 to 31
Calculation steps:
[( 31 - 171 ) ÷ 171] x 100 = -81.87%
Formula
Percentage change = [(31 - 171) / 171] x 100
Subtract the new number by the original number
31 - 171 = -140
-140 ÷ 171 = -0.8187134502923976
-0.8187134502923976 x 100 = -81.87%