-39.29% is the change from 509 to 309
Calculation steps:
[( 309 - 509 ) ÷ 509] x 100 = -39.29%
Formula
Percentage change = [(309 - 509) / 509] x 100
Subtract the new number by the original number
309 - 509 = -200
-200 ÷ 509 = -0.3929273084479371
-0.3929273084479371 x 100 = -39.29%