Let’s assume initial population of state X is X’
Initial population of state Y is Y’
Initial ratio P1 = X’/Y’
New population of state X is : X’ (1 + x/100)
New population of state X=Y is : Y’ (1 + y/100)
New ratio P2 = [X’(1+x/100)] / [Y’(1+y/100)]
Change in ratio = [ P2 – P1 ] / P1 = [ (1 + x/100) / (1 + y/100) ] – 1
Solving this will give , (x-y) / (100+y)
Percentage increased , 100 * (x-y) / (100+y)