-2.6% is the change from 655 to 638
Calculation steps:
[( 638 - 655 ) ÷ 655] x 100 = -2.6%
Formula
Percentage change = [(638 - 655) / 655] x 100
Subtract the new number by the original number
638 - 655 = -17
-17 ÷ 655 = -0.025954198473282442
-0.025954198473282442 x 100 = -2.6%