-98.6% is the change from 931 to 13
Calculation steps:
[( 13 - 931 ) ÷ 931] x 100 = -98.6%
Formula
Percentage change = [(13 - 931) / 931] x 100
Subtract the new number by the original number
13 - 931 = -918
-918 ÷ 931 = -0.9860365198711063
-0.9860365198711063 x 100 = -98.6%