Why there is an income gap

Five people in a household working make more money than one person working part time.

Households with two full-time workers earn five times as much as households in which nobody works.

Here is a summary  (from 2010) of some of the key demographic differences between American households in the bottom and top income quintiles in 2010:

1. On average, there were significantly more income earners per household in the top income quintile households (1.97) than earners per household in the lowest-income households (0.43).

2. Married-couple households represented a much greater share of the top income quintile (78.4 percent) than for the bottom income quintile (17 percent), and single-parent or single households represented a much greater share of the bottom quintile (83 percent) than for the top quintile (21.6 percent).

3. Roughly 3 out of 4 households in the top income quintile included individuals in their prime earning years between the ages of 35-64, compared to only 43.6 percent of household members in the bottom fifth who were in that age group.

4. Compared to members of the top income quintile, household members in the bottom income quintile were 1.6 times more likely to be in the youngest age group (under 35 years), and three times more likely to be in the oldest age group (65 years and over).

5. More than four times as many top quintile households included at least one adult who was working full-time in 2010 (77.2 percent) compared to the bottom income quintile (only 17.4 percent), and more than five times as many households in the bottom quintile included adults who did not work at all (68.2 percent) compared to top quintile households whose family members did not work (13.3 percent).

6. Family members of households in the top income quintile were about five times more likely to have a college degree (60.3 percent) than members of households in the bottom income quintile (only 12.1 percent). In contrast, family members of the lowest income quintile were 12 times more likely than those in the top income quintile to have less than a high school degree in 2010 (26.7 percent vs. 2.2 percent).