Spending Hidden in the Tax Code

The blue line is total discretionary outlays of the federal government, and the brown line is the sum of tax expenditures.  Both are in constant dollars.  Note that these two categories of spending are about equal in magnitude.  It is just as important to focus on stealth spending implemented through the tax code as on explicit spending.

Source.

Addendum: David Leonhardt has a related article in the Times today.