Sales taxes usually only apply to certain purchases, not all purchases and thus don't act like an income tax, and most states and localities with an income tax have a progressive one with the usual deductions, same as federal, you're implying a tax on top of the federal of 22.65% for people making 15k a year, and that's just not the case. Assuming the state even had a flat income tax, as opposed to none or a progressive one, they'd still have less than 15k as taxable income and a number of purchases which weren't sales taxed. The implication someone making 15k is paying $3,400 in SS, State/local and sales tax is just not accurate. Its not non-zero [assuming they aren't getting money in the form of earned income credits or welfare] but it's likely to mostly be in the form of gas tax, sales tax on soda/beer/cigs, various luxuries, etc. Food and second hand items normally aren't sales taxed and in some states neither is clothing or some other items.