3.15% is the change from 666 to 687
Calculation steps:
[( 687 - 666 ) ÷ 666] x 100 = 3.15%
Formula
Percentage change = [(687 - 666) / 666] x 100
Subtract the new number by the original number
687 - 666 = 21
21 ÷ 666 = 0.03153153153153153
0.03153153153153153 x 100 = 3.15%