>As another poster pointed out, some people with low income pay a negative income tax.
The only way income tax can be negative, is if it includes low income benefits. In any case, no matter how one chooses to define things, isn't my argument clear at this point: Increasing benefits or decreasing taxes are more efficient than increasing the minimum wage.
I think the confusion is over the term "benefits". In the usage I've seen, benefits includes things not directly associated with the income tax code, like say, food stamps. If you increase your income, you may lose access to food stamps, but the food stamps don't come with your income tax returns and receiving them is part of a separate application process in most (all?) states.
So when you said income tax, I thought you were including those kinds of programs. But it sounds like you mean something closer to "benefits and deductions" directly in the tax code, like the earned income tax credit.