-87.35% is the change from 166 to 21
Calculation steps:
[( 21 - 166 ) ÷ 166] x 100 = -87.35%
Formula
Percentage change = [(21 - 166) / 166] x 100
Subtract the new number by the original number
21 - 166 = -145
-145 ÷ 166 = -0.8734939759036144
-0.8734939759036144 x 100 = -87.35%