-66.4% is the change from 509 to 171
Calculation steps:
[( 171 - 509 ) ÷ 509] x 100 = -66.4%
Formula
Percentage change = [(171 - 509) / 509] x 100
Subtract the new number by the original number
171 - 509 = -338
-338 ÷ 509 = -0.6640471512770137
-0.6640471512770137 x 100 = -66.4%