-50% is the change from 166 to 83
Calculation steps:
[( 83 - 166 ) ÷ 166] x 100 = -50%
Formula
Percentage change = [(83 - 166) / 166] x 100
Subtract the new number by the original number
83 - 166 = -83
-83 ÷ 166 = -0.5
-0.5 x 100 = -50%
Example