What this ranking compares
Every state and the District of Columbia, worked out on the same gross salary and the same filing status, each with the same official withholding rules its own salary page uses. The keep rate is the share of the salary left after every payroll deduction: federal income tax, Social Security, Medicare, and whatever the state adds. The effective rate beside it is the same figure seen from the other side, the share that goes.
A ranking only means something if nothing moves but the thing being ranked. So every state gets the same answers to every question its calculator asks: no children, the default number of allowances, and the default county or city where a state has a local tax that depends on where you live. Change any of those and a state can move a few places; the state's own page lets you set them.
Why the chart measures what the state takes
Federal income tax, Social Security and Medicare do not depend on where you work. Two people on the same salary with the same filing status have the same federal lines on their payslip in Texas and in California, to the cent, because every state starts from the same federal rules. Everything that separates one state from another happens in the state's own layer.
That is why the bars measure what the state takes rather than the keep rate. Keep rates sit close together, because the federal part they share is most of what leaves a payslip, and bars of nearly equal length hide the ranking they are meant to show. The state's share starts at nothing, so measured on its own the differences between states show at their true size. The keep rate is still in the table, next to the effective rate, for anyone who wants the whole picture.
Why several states tie at the top
A state with no tax on wages and no payroll levy of its own adds nothing to the federal lines, so every such state leaves exactly the same pay. They are not close; they are identical, and the ranking gives them one shared place rather than inventing an order among them.
At lower salaries the group can grow. A state whose allowances or standard deduction are larger than the salary takes nothing either, and it joins the top for as long as that lasts.
No income tax is not the same as no deductions
Some states run insurance funds paid for through the payroll: disability insurance, paid family leave, long-term care, or an employee share of unemployment insurance. Those levies leave the payslip exactly the way a tax does, so they count in what the state takes.
That is how a state with no income tax at all can rank below the top group. Alaska and Washington are the two on file: neither taxes wages, and both take a levy that the states at the top do not.
What the figures leave out
These are withholding figures for a full year of employment, not tax returns. They leave out what only appears when a return is filed: itemised deductions, credits that depend on the whole household, investment income, and refunds.
They also leave out pre-tax deductions such as retirement plan contributions and health insurance premiums, which lower the taxable wage in every state but by an amount that depends on the job rather than on the place. City and county income taxes are included only where the state's calculator models them. A state whose own page carries a note about something like that is marked in the table, and the note itself is on that page.
Arizona is the one state whose figure is a tax bill rather than an amount withheld. Arizona lets employees choose their own withholding percentage, so there is no single withheld amount to show; the page uses what the state's tax on that salary works out to, which is the fairer figure to rank.
Europe, beside rather than inside
The European countries are worked out on the same figure in their own currency and shown in a block of their own. A hundred thousand euros and a hundred thousand dollars are not the same amount of money, and a single league table has no room for the sentence that would make them comparable. What the block does show fairly is how much of the same nominal salary each tax system leaves, which is a question about the systems rather than about pay.
To compare what a salary is worth in two places once prices and exchange rates are taken into account, the salary comparison does that step, and the cost of living comparison does it for spending rather than for pay.
What this is not
A ranking of where to live. The state that takes the least from a salary can still cost more to live in, and the one that takes the most can be where the salary itself is higher. This page answers one question, how much of the same pay each state's rules leave you, and it answers it exactly.