-81% is the change from 521 to 99
Calculation steps:
[( 99 - 521 ) ÷ 521] x 100 = -81%
Formula
Percentage change = [(99 - 521) / 521] x 100
Subtract the new number by the original number
99 - 521 = -422
-422 ÷ 521 = -0.8099808061420346
-0.8099808061420346 x 100 = -81%