-18.88% is the change from 821 to 666
Calculation steps:
[( 666 - 821 ) ÷ 821] x 100 = -18.88%
Formula
Percentage change = [(666 - 821) / 821] x 100
Subtract the new number by the original number
666 - 821 = -155
-155 ÷ 821 = -0.18879415347137637
-0.18879415347137637 x 100 = -18.88%