-12.11% is the change from 999 to 878
Calculation steps:
[( 878 - 999 ) ÷ 999] x 100 = -12.11%
Formula
Percentage change = [(878 - 999) / 999] x 100
Subtract the new number by the original number
878 - 999 = -121
-121 ÷ 999 = -0.12112112112112113
-0.12112112112112113 x 100 = -12.11%