-84.45% is the change from 521 to 81
Calculation steps:
[( 81 - 521 ) ÷ 521] x 100 = -84.45%
Formula
Percentage change = [(81 - 521) / 521] x 100
Subtract the new number by the original number
81 - 521 = -440
-440 ÷ 521 = -0.8445297504798465
-0.8445297504798465 x 100 = -84.45%