-2.88% is the change from 521 to 506
Calculation steps:
[( 506 - 521 ) ÷ 521] x 100 = -2.88%
Formula
Percentage change = [(506 - 521) / 521] x 100
Subtract the new number by the original number
506 - 521 = -15
-15 ÷ 521 = -0.028790786948176585
-0.028790786948176585 x 100 = -2.88%