-18.53% is the change from 815 to 664
Calculation steps:
[( 664 - 815 ) ÷ 815] x 100 = -18.53%
Formula
Percentage change = [(664 - 815) / 815] x 100
Subtract the new number by the original number
664 - 815 = -151
-151 ÷ 815 = -0.18527607361963191
-0.18527607361963191 x 100 = -18.53%