-8.7% is the change from 23 to 21
Calculation steps:
[( 21 - 23 ) ÷ 23] x 100 = -8.7%
Formula
Percentage change = [(21 - 23) / 23] x 100
Subtract the new number by the original number
21 - 23 = -2
-2 ÷ 23 = -0.08695652173913043
-0.08695652173913043 x 100 = -8.7%