-6.61% is the change from 878 to 820
Calculation steps:
[( 820 - 878 ) ÷ 878] x 100 = -6.61%
Formula
Percentage change = [(820 - 878) / 878] x 100
Subtract the new number by the original number
820 - 878 = -58
-58 ÷ 878 = -0.06605922551252848
-0.06605922551252848 x 100 = -6.61%