-18.64% is the change from 821 to 668
Calculation steps:
[( 668 - 821 ) ÷ 821] x 100 = -18.64%
Formula
Percentage change = [(668 - 821) / 821] x 100
Subtract the new number by the original number
668 - 821 = -153
-153 ÷ 821 = -0.18635809987819732
-0.18635809987819732 x 100 = -18.64%