-51.2% is the change from 166 to 81
Calculation steps:
[( 81 - 166 ) ÷ 166] x 100 = -51.2%
Formula
Percentage change = [(81 - 166) / 166] x 100
Subtract the new number by the original number
81 - 166 = -85
-85 ÷ 166 = -0.5120481927710844
-0.5120481927710844 x 100 = -51.2%