-50.31% is the change from 638 to 317
Calculation steps:
[( 317 - 638 ) ÷ 638] x 100 = -50.31%
Formula
Percentage change = [(317 - 638) / 638] x 100
Subtract the new number by the original number
317 - 638 = -321
-321 ÷ 638 = -0.5031347962382445
-0.5031347962382445 x 100 = -50.31%