-1.21% is the change from 990 to 978
Calculation steps:
[( 978 - 990 ) ÷ 990] x 100 = -1.21%
Formula
Percentage change = [(978 - 990) / 990] x 100
Subtract the new number by the original number
978 - 990 = -12
-12 ÷ 990 = -0.012121212121212121
-0.012121212121212121 x 100 = -1.21%