-3.93% is the change from 331 to 318
Calculation steps:
[( 318 - 331 ) ÷ 331] x 100 = -3.93%
Formula
Percentage change = [(318 - 331) / 331] x 100
Subtract the new number by the original number
318 - 331 = -13
-13 ÷ 331 = -0.03927492447129909
-0.03927492447129909 x 100 = -3.93%