-33.51% is the change from 961 to 639
Calculation steps:
[( 639 - 961 ) ÷ 961] x 100 = -33.51%
Formula
Percentage change = [(639 - 961) / 961] x 100
Subtract the new number by the original number
639 - 961 = -322
-322 ÷ 961 = -0.3350676378772112
-0.3350676378772112 x 100 = -33.51%