-96.7% is the change from 637 to 21
Calculation steps:
[( 21 - 637 ) ÷ 637] x 100 = -96.7%
Formula
Percentage change = [(21 - 637) / 637] x 100
Subtract the new number by the original number
21 - 637 = -616
-616 ÷ 637 = -0.967032967032967
-0.967032967032967 x 100 = -96.7%