-19.39% is the change from 521 to 420
Calculation steps:
[( 420 - 521 ) ÷ 521] x 100 = -19.39%
Formula
Percentage change = [(420 - 521) / 521] x 100
Subtract the new number by the original number
420 - 521 = -101
-101 ÷ 521 = -0.19385796545105566
-0.19385796545105566 x 100 = -19.39%