Explaining Income Inequality With Demographics.

This is an updated chart from the Census Bureau's report Income and Poverty in the United States: 2015. What it shows is that differences in household income are primarily related to differences in the households themselves.

1. High income households earn more because they have more people in them who are actually working at something.
2. High income households have a much higher rate of marriage.
3. High income households are composed of better educated people, who have higher earning capabilities.
4. High income households have more people in their peak earning years (35-64).

In other words, contrary to popular political rhetoric, household income inequality is not something that is "done to you", it is mostly a product of decisions that you have made and where you are in life stage. The good news is that these are factors that you can influence. You can choose more education. You can choose to work. You can choose to marry and have more earners in your household. And if you're 25 you will eventually be 35 or 40 (sorry, but if you're 65, your earning power won't increase with age).  

Also, keep in mind that "income" here is only earned cash income. It does not include transfer payments (e.g. welfare, Medicaid, social security, housing subsidies, etc.)