The document you link to says: The marginal tax rates include the combined effects of federal and state individual income taxes, federal payroll taxes, a

The document you link to says: The marginal tax rates include the combined effects of federal and state individual income taxes, federal payroll taxes, and benefits from the Supplemental Nutrition Assistance Program and cost-sharing subsidies for health insurance, generally on the basis of 2016 law. Unfortunately, SNAP and ACA health insurance subsidies are not the only means-tested welfare bits, and the other ones are _not_ being included here. Most prominently missing are Medicaid, TANF, and Section 8 housing, but there are a _lot_ of means-tested programs (e.g. Pell Grants) that only apply to certain households. Now I do think it's true that the income ranges where the effective marginal "tax" rate is over 100% are fairly narrow for most households. But the ranges where the rates are less than 100% but not much less are far wider. And that gives you an effective take-home hourly wage that is tiny. If you happen to have kids, it almost certainly doesn't cover daycare costs, for example...