-82.74% is the change from 991 to 171
Calculation steps:
[( 171 - 991 ) ÷ 991] x 100 = -82.74%
Formula
Percentage change = [(171 - 991) / 991] x 100
Subtract the new number by the original number
171 - 991 = -820
-820 ÷ 991 = -0.82744702320888
-0.82744702320888 x 100 = -82.74%