Original: The median household income rose by 30% while the income for the 20th percentile (the lower threshold for the second lowest quintile) rose by only 28% from $14,002 to $17,984.
Simplified: The median household income rose by 30% while the income for the 20th percentile (the lower threshold for the second lowest quitile) rose by only 28% from $14,002 to $17,984.