-2.1% is the change from 857 to 839
Calculation steps:
[( 839 - 857 ) ÷ 857] x 100 = -2.1%
Formula
Percentage change = [(839 - 857) / 857] x 100
Subtract the new number by the original number
839 - 857 = -18
-18 ÷ 857 = -0.021003500583430573
-0.021003500583430573 x 100 = -2.1%