-86.44% is the change from 671 to 91
Calculation steps:
[( 91 - 671 ) ÷ 671] x 100 = -86.44%
Formula
Percentage change = [(91 - 671) / 671] x 100
Subtract the new number by the original number
91 - 671 = -580
-580 ÷ 671 = -0.8643815201192251
-0.8643815201192251 x 100 = -86.44%