-2.7% is the change from 666 to 648
Calculation steps:
[( 648 - 666 ) ÷ 666] x 100 = -2.7%
Formula
Percentage change = [(648 - 666) / 666] x 100
Subtract the new number by the original number
648 - 666 = -18
-18 ÷ 666 = -0.02702702702702703
-0.02702702702702703 x 100 = -2.7%