-87.72% is the change from 171 to 21
Calculation steps:
[( 21 - 171 ) ÷ 171] x 100 = -87.72%
Formula
Percentage change = [(21 - 171) / 171] x 100
Subtract the new number by the original number
21 - 171 = -150
-150 ÷ 171 = -0.8771929824561403
-0.8771929824561403 x 100 = -87.72%