-17.82% is the change from 999 to 821
Calculation steps:
[( 821 - 999 ) ÷ 999] x 100 = -17.82%
Formula
Percentage change = [(821 - 999) / 999] x 100
Subtract the new number by the original number
821 - 999 = -178
-178 ÷ 999 = -0.1781781781781782
-0.1781781781781782 x 100 = -17.82%