Final answer:
In 2006, the poorest 20% of the US population received less than 5% of all national income, which illustrates significant income inequality.
Step-by-step explanation:
In 2006, the poorest 20% of the US population received less than 5% of all national income. According to the provided income distribution data by quintile for the United States, the bottom quintile of the income distribution received notably low percentages of national income over the years. For example, in 2011, which is close to the 2006 figure in question, the bottom quintile received only 3.2% of total income. This disparity highlights the issue of income inequality in the U.S. and the concentration of wealth within the highest quintiles, particularly among the top 5% of earners.