Congressional Budget Office, Refundable Tax Credits:

The number and total costs of the refundable credits in
the income tax system have grown considerably since
1975. The number of credits peaked at 11 in 2010 before
dropping to 6 in 2013 (see Figure 1). Their total costs
(that is, the reduction in revenues and the increase in
outlays) reached a high of $238 billion in 2008. (That
amount and other annual costs discussed in this report
are expressed in 2013 dollars.) Those costs will drop to
$149 billion in 2013, the CBO estimates, mostly for the earned income tax credit
(EITC) and the child tax credit. By 2018, three more
credits will have expired, and the EITC and the child tax
credit will have been scaled back.

Those cutbacks in refundable tax credits will be more
than offset, however, by new health-related subsidies
provided through the tax system. Starting in 2014, a
new refundable tax credit will be available to some people
for the purchase of health insurance through newly
created exchanges. The cost of that credit will be about. $110 billion by 2021, CBO and the staff of the Joint
Committee on Taxation (JCT) project, bringing the total
cost of refundable tax credits in that year to $213 billion—
roughly the same as the costs in 2009 and 2010,
even though the number of refundable tax credits will
have fallen by more than half between 2010 and 2021.