While a certain degree of income inequality might be expected, the difference between rich and poor Americans has grown dramatically in recent years. As of 2013, the wealthiest 20% of Americans had more income in aggregate than the bottom 80% combined.

State and local tax systems play a significant role in redistributing income among people. The nationwide average effective tax rate for the poorest 20% of Americans was 10.9%, roughly double the 5.4% rate for the top 1%.

Click here to see the states with the worst taxes for the average American

When looking at taxes paid as a share of the income earned, all states have a regressive tax system, which means poorer residents are taxed more than the wealthiest ones. The difference in effective tax rates between income groups, however, varies widely between states. According to “Who Pays? A Distributional Analysis of the Tax Systems in All 50 States,” a report released by the Institute on Taxation and Economic Policy (ITEP), Washington has by far the most regressive tax system nationwide. Based on the index score, a ratio calculated from a range of factors to measure income inequality before and after taxes, these are the states with the most unfair tax systems for the average American.

In fact, the poorest 20% of individuals paid at least 12% of their total incomes in state and local taxes in seven of the 10 states with the most regressive tax systems. In contrast, the wealthiest 1% of residents paid no more than 3% in state and local taxes as a share of income in six of the 10 states. In an interview with 24/7 Wall St., Meg Wiehe, state tax policy director at ITEP, said that in most states, and these 10 especially, “tax distribution looks very much like a staircase going down, where as your income goes up, your effective tax rate goes down.”

State residents earning average incomes also often bore a higher tax burden compared to the richest residents. The middle 60% of earners in all of the 10 states paid at least three times what the wealthiest 1% paid, as a share of income, in state and local taxes — all of these ratios were also among the highest nationwide. Middle earners in Washington and Florida, the two most regressive taxation states, paid as a share of their income more than 400% what the richest 1% of residents paid as a share of their income.

Often, it’s the presence or absence of a particular kind of tax that determines the extent to which state tax systems are regressive. For example, taxing goods and services consumed daily such as food is especially regressive because food makes up a much larger share of poorer Americans’ income. A graduated income tax is far more progressive, on the other hand. Five of the 10 states with unfair tax systems taxed food at the state and local level. Also, all but one of the 10 states had relatively low or flat income tax rates, and four had no personal income tax.

According to Wiehe, these states “rely heavily on taxes that are paid disproportionately by low- and middle-income households, and have very little reliance on taxes that the top 1% or top 5% would be responsible for paying.” In other words, states have to make up for that revenue in one way or another. Nationwide, personal and corporate income taxes accounted for an average of nearly 18% of state revenue. Yet in five of the 10 states, the contribution to revenue from income taxes was less than 5%. And while sales and excise taxes accounted for less than one quarter of state revenue on average across the nation, they accounted for more than 30% of revenue in six of the 10 states with the most regressive tax policies.

While it is difficult to know the exact degree that these tax policies impact income inequality, the states with the most regressive tax systems also had relatively uneven income distribution even before taxes were applied. In six of the 10 states, the 2013 Gini coefficient — which has values between zero and one, where one means all income belongs to a single person and zero means uniform income distribution — was higher than in the majority of states.

To identify the 10 states with the worst tax systems for average Americans, 24/7 Wall St. reviewed ITEP’s Tax Inequality Index scores for the 50 states. The index incorporated effective tax rates for the poorest 20%, middle 60%, top 1%, as well as ratios comparing these rates, among other measures. Effective tax rates were based on total state and local taxes as a share of family income for non-elderly taxpayers in all 50 states. ITEP’s model used 2012 income figures, and considered tax laws from 2014 and 2015. Contributions to state revenue by tax type were also provided by ITEP. We reviewed the Gini coefficient from 2013 — which is based on pre-tax income — as well as additional economic data from the Census Bureau’s 2013 American Community Survey.

These are the states with the worst taxes for the average American.