-99.75% is the change from 400 to 1
Calculation steps:
[( 1 - 400 ) ÷ 400] x 100 = -99.75%
Formula
Percentage change = [(1 - 400) / 400] x 100
Subtract the new number by the original number
1 - 400 = -399
-399 ÷ 400 = -0.9975
-0.9975 x 100 = -99.75%
Example