-84.98% is the change from 666 to 100
Calculation steps:
[( 100 - 666 ) ÷ 666] x 100 = -84.98%
Formula
Percentage change = [(100 - 666) / 666] x 100
Subtract the new number by the original number
100 - 666 = -566
-566 ÷ 666 = -0.8498498498498499
-0.8498498498498499 x 100 = -84.98%