-87.93% is the change from 671 to 81
Calculation steps:
[( 81 - 671 ) ÷ 671] x 100 = -87.93%
Formula
Percentage change = [(81 - 671) / 671] x 100
Subtract the new number by the original number
81 - 671 = -590
-590 ÷ 671 = -0.879284649776453
-0.879284649776453 x 100 = -87.93%