-9.52% is the change from 21 to 19
Calculation steps:
[( 19 - 21 ) ÷ 21] x 100 = -9.52%
Formula
Percentage change = [(19 - 21) / 21] x 100
Subtract the new number by the original number
19 - 21 = -2
-2 ÷ 21 = -0.09523809523809523
-0.09523809523809523 x 100 = -9.52%