“ IN GENERAL- In the case of a taxpayer whose household income is less than 400 percent of the poverty line for the size of the family involved for the taxable year, the amount of the increase under subparagraph (A) shall in no event exceed the applicable dollar amount determined in accordance with the following table (one-half of such amount in the case of a taxpayer whose tax is determined under section 1 (c) for the taxable year) : (b) Effective Date.— The amendment made by this section shall apply to taxable years ending after December 31, 2013. ”