-97.9% is the change from 998 to 21
Calculation steps:
[( 21 - 998 ) ÷ 998] x 100 = -97.9%
Formula
Percentage change = [(21 - 998) / 998] x 100
Subtract the new number by the original number
21 - 998 = -977
-977 ÷ 998 = -0.9789579158316634
-0.9789579158316634 x 100 = -97.9%