3.45% is the change from 521 to 539
Calculation steps:
[( 539 - 521 ) ÷ 521] x 100 = 3.45%
Formula
Percentage change = [(539 - 521) / 521] x 100
Subtract the new number by the original number
539 - 521 = 18
18 ÷ 521 = 0.0345489443378119
0.0345489443378119 x 100 = 3.45%