-50% is the change from 318 to 159
Calculation steps:
[( 159 - 318 ) ÷ 318] x 100 = -50%
Formula
Percentage change = [(159 - 318) / 318] x 100
Subtract the new number by the original number
159 - 318 = -159
-159 ÷ 318 = -0.5
-0.5 x 100 = -50%
Example