-17.76% is the change from 991 to 815
Calculation steps:
[( 815 - 991 ) ÷ 991] x 100 = -17.76%
Formula
Percentage change = [(815 - 991) / 991] x 100
Subtract the new number by the original number
815 - 991 = -176
-176 ÷ 991 = -0.17759838546922302
-0.17759838546922302 x 100 = -17.76%