Given conditions are :
In 1980's, a typical middle-income household earned= $34,757
In 2009, a similar middle-income household earned= $38,550
And we have to find relative increase in income for these households from 1980 to 2009.
So first we will find the total increase in amounts.
Relative increase =
= 10.91% or rounding it off we get approx 11%.
Hence, the answer is 11%.