-89.9% is the change from 990 to 100
Calculation steps:
[( 100 - 990 ) ÷ 990] x 100 = -89.9%
Formula
Percentage change = [(100 - 990) / 990] x 100
Subtract the new number by the original number
100 - 990 = -890
-890 ÷ 990 = -0.898989898989899
-0.898989898989899 x 100 = -89.9%