-83.49% is the change from 521 to 86
Calculation steps:
[( 86 - 521 ) ÷ 521] x 100 = -83.49%
Formula
Percentage change = [(86 - 521) / 521] x 100
Subtract the new number by the original number
86 - 521 = -435
-435 ÷ 521 = -0.8349328214971209
-0.8349328214971209 x 100 = -83.49%