-17.26% is the change from 991 to 820
Calculation steps:
[( 820 - 991 ) ÷ 991] x 100 = -17.26%
Formula
Percentage change = [(820 - 991) / 991] x 100
Subtract the new number by the original number
820 - 991 = -171
-171 ÷ 991 = -0.17255297679112008
-0.17255297679112008 x 100 = -17.26%