-87.78% is the change from 990 to 121
Calculation steps:
[( 121 - 990 ) ÷ 990] x 100 = -87.78%
Formula
Percentage change = [(121 - 990) / 990] x 100
Subtract the new number by the original number
121 - 990 = -869
-869 ÷ 990 = -0.8777777777777778
-0.8777777777777778 x 100 = -87.78%