-33.1% is the change from 991 to 663
Calculation steps:
[( 663 - 991 ) ÷ 991] x 100 = -33.1%
Formula
Percentage change = [(663 - 991) / 991] x 100
Subtract the new number by the original number
663 - 991 = -328
-328 ÷ 991 = -0.33097880928355194
-0.33097880928355194 x 100 = -33.1%