-19.61% is the change from 821 to 660
Calculation steps:
[( 660 - 821 ) ÷ 821] x 100 = -19.61%
Formula
Percentage change = [(660 - 821) / 821] x 100
Subtract the new number by the original number
660 - 821 = -161
-161 ÷ 821 = -0.1961023142509135
-0.1961023142509135 x 100 = -19.61%