-2.3% is the change from 521 to 509
Calculation steps:
[( 509 - 521 ) ÷ 521] x 100 = -2.3%
Formula
Percentage change = [(509 - 521) / 521] x 100
Subtract the new number by the original number
509 - 521 = -12
-12 ÷ 521 = -0.023032629558541268
-0.023032629558541268 x 100 = -2.3%