-50% is the change from 4 to 2
Calculation steps:
[( 2 - 4 ) ÷ 4] x 100 = -50%
Formula
Percentage change = [(2 - 4) / 4] x 100
Subtract the new number by the original number
2 - 4 = -2
-2 ÷ 4 = -0.5
-0.5 x 100 = -50%
Example