Details keep coming in about "Plan B," House Speaker John Boehner's proposal to extend the Bush tax cuts for income under $1 million permanently. A lot gets extended. The current very low estate tax rates are made permanent, and the phase-out of the personal exemption for high earners, and the "Pease" limit on high earners' itemized deductions, are completely eliminated.

But some features don't get extended. While the bill makes permanent the expansion of the Child Tax Credit (CTC) signed into law by George W. Bush as part of the 2001 tax cut deal — which bumped the credit from $500 to $1,000 — it does not extend an expansion that was passed as part of the 2009 stimulus package, and has been renewed since then, allowing poor families to refund more of the credit. Nor does it extend the stimulus's expansion of the Earned Income Tax Credit (EITC), by far the most important anti-poverty program the federal government has, or the American Opportunity Credit (AOC), which provides tuition assistance for middle-class families.

That has a huge impact on lower-income families. The Tax Policy Center hasn't projected the distributional effect of extending the AOC, but it has estimated those effects for the stimulus expansions of EITC and CTC:

The working poor, on average, would see taxes go up between $1,000 and $1,500 dollars. Barely anyone making over $100,000 would see a tax increase, and as a percentage of income, middle and upper middle class people making between $40,000 and $100,000 a year would see taxes go up less. But low income families earning $10,000 to $30,000 a year really take a beating under Boehner's plan. Of course, if we do nothing, then the 2001 provisions expire as well and poor families are really in for a bruising.