-1.93% is the change from 831 to 815
Calculation steps:
[( 815 - 831 ) ÷ 831] x 100 = -1.93%
Formula
Percentage change = [(815 - 831) / 831] x 100
Subtract the new number by the original number
815 - 831 = -16
-16 ÷ 831 = -0.019253910950661854
-0.019253910950661854 x 100 = -1.93%