-39.75% is the change from 815 to 491
Calculation steps:
[( 491 - 815 ) ÷ 815] x 100 = -39.75%
Formula
Percentage change = [(491 - 815) / 815] x 100
Subtract the new number by the original number
491 - 815 = -324
-324 ÷ 815 = -0.39754601226993863
-0.39754601226993863 x 100 = -39.75%