-92.18% is the change from 639 to 50
Calculation steps:
[( 50 - 639 ) ÷ 639] x 100 = -92.18%
Formula
Percentage change = [(50 - 639) / 639] x 100
Subtract the new number by the original number
50 - 639 = -589
-589 ÷ 639 = -0.9217527386541471
-0.9217527386541471 x 100 = -92.18%