-19.19% is the change from 99 to 80
Calculation steps:
[( 80 - 99 ) ÷ 99] x 100 = -19.19%
Formula
Percentage change = [(80 - 99) / 99] x 100
Subtract the new number by the original number
80 - 99 = -19
-19 ÷ 99 = -0.1919191919191919
-0.1919191919191919 x 100 = -19.19%