-12.21% is the change from 991 to 870
Calculation steps:
[( 870 - 991 ) ÷ 991] x 100 = -12.21%
Formula
Percentage change = [(870 - 991) / 991] x 100
Subtract the new number by the original number
870 - 991 = -121
-121 ÷ 991 = -0.12209889001009082
-0.12209889001009082 x 100 = -12.21%