-86.34% is the change from 666 to 91
Calculation steps:
[( 91 - 666 ) ÷ 666] x 100 = -86.34%
Formula
Percentage change = [(91 - 666) / 666] x 100
Subtract the new number by the original number
91 - 666 = -575
-575 ÷ 666 = -0.8633633633633634
-0.8633633633633634 x 100 = -86.34%