-0.73% is the change from 821 to 815
Calculation steps:
[( 815 - 821 ) ÷ 821] x 100 = -0.73%
Formula
Percentage change = [(815 - 821) / 821] x 100
Subtract the new number by the original number
815 - 821 = -6
-6 ÷ 821 = -0.007308160779537149
-0.007308160779537149 x 100 = -0.73%