-3.84% is the change from 521 to 501
Calculation steps:
[( 501 - 521 ) ÷ 521] x 100 = -3.84%
Formula
Percentage change = [(501 - 521) / 521] x 100
Subtract the new number by the original number
501 - 521 = -20
-20 ÷ 521 = -0.03838771593090211
-0.03838771593090211 x 100 = -3.84%