3.1% is the change from 646 to 666
Calculation steps:
[( 666 - 646 ) ÷ 646] x 100 = 3.1%
Formula
Percentage change = [(666 - 646) / 646] x 100
Subtract the new number by the original number
666 - 646 = 20
20 ÷ 646 = 0.030959752321981424
0.030959752321981424 x 100 = 3.1%