I’m not talking about the similarity of the taxes but of the similarity of the argument: why should “I” pay more than, or the same amount as, the taxes of someone with a larger family? The argument in each case assures or protects long-term general welfare—one of a nation, the other of a school district.
People already pay more taxes than those with families, but Santorum’s plan would significantly lessen incentives for work for approximately half the population.
That’s not good economic policy aside from any ‘fairness’ argument. And tere’s more evidence by far of tax policy influencing economic behavior than family formation—just look at the experience in Europe.