The efficacy of these taxes are amply demonstrated by their extremely regressive nature.  For instance, the payroll taxes for Social Security and Medicare/Medicaid hit the lowest income folks the hardest.  They’re taxed at the same nominal rate as everyone else (except the well-off in the case of Social Security: there’s an upper limit on the income taxable for this purpose).

However.

Someone making the Federal Poverty Guideline income ($22,350 for a man in a four-person family in 2011) was taxed at 4.2% of that income (6.2% when the cut expires next January, but we’ll stick to the lower rate here)—$938.70.  A man making $100,000 paid a tax of $4,200, including that same $938.70 on his first $22,350 of income.  Who do you suppose was hit harder by that $939 tax?

The poor man already is living at the edge of his income; the dollar taxed to him—the very same dollar that is taxed to our better off man—is far more important to the poor man.

So it is with income taxes, whether those taxes are for Article 8 purposes, or some of them are for other government-determined—social engineering—purposes.

Legitimate taxes must be evaluated for their impact on what Wretchard of Belmont Club has described as the design margin: how much safety is left for handling the unforeseen when a tax dollar is taken away from a man?

The correction, of course, is not to raise taxes on everyone else—the well-off already are paying far more than their share, while the half [sic] at the “bottom” of the distribution are paying next to nothing.  Moreover, this would do nothing to reduce the importance of those tax dollars that are in the poor man’s margin of safety between what he has and what he needs for an emergency.  No, the answer is to lower tax rates—to increase the width of the design margin—and to move to a flat tax with no deductions.  Taxation for government-mandated social engineering purposes just hammers at that design margin, shrinking it, no matter the good intentions behind the assessment.

A tax dollar always will be more important to the poor man than to the better off man; no amount of attempted progressivity in a tax code will reduce this.  A flat tax will reduce the difference in relative importance, though.