-96.8% is the change from 657 to 21
Calculation steps:
[( 21 - 657 ) ÷ 657] x 100 = -96.8%
Formula
Percentage change = [(21 - 657) / 657] x 100
Subtract the new number by the original number
21 - 657 = -636
-636 ÷ 657 = -0.9680365296803652
-0.9680365296803652 x 100 = -96.8%