-1.31% is the change from 991 to 978
Calculation steps:
[( 978 - 991 ) ÷ 991] x 100 = -1.31%
Formula
Percentage change = [(978 - 991) / 991] x 100
Subtract the new number by the original number
978 - 991 = -13
-13 ÷ 991 = -0.013118062563067608
-0.013118062563067608 x 100 = -1.31%