-2.1% is the change from 858 to 840
Calculation steps:
[( 840 - 858 ) ÷ 858] x 100 = -2.1%
Formula
Percentage change = [(840 - 858) / 858] x 100
Subtract the new number by the original number
840 - 858 = -18
-18 ÷ 858 = -0.02097902097902098
-0.02097902097902098 x 100 = -2.1%