-57.96% is the change from 999 to 420
Calculation steps:
[( 420 - 999 ) ÷ 999] x 100 = -57.96%
Formula
Percentage change = [(420 - 999) / 999] x 100
Subtract the new number by the original number
420 - 999 = -579
-579 ÷ 999 = -0.5795795795795796
-0.5795795795795796 x 100 = -57.96%