-99.1% is the change from 1000 to 9
Calculation steps:
[( 9 - 1000 ) ÷ 1000] x 100 = -99.1%
Formula
Percentage change = [(9 - 1000) / 1000] x 100
Subtract the new number by the original number
9 - 1000 = -991
-991 ÷ 1000 = -0.991
-0.991 x 100 = -99.1%