The latest Congressional Budget Office projection suggests that GDP in 2016 will be $19.1 trillion. Sixteen percent of that is about $3.1 trillion. But, based on CBO figures, non-defense spending will be about $3.6 trillion in 2016. So to meet his goals, Romney would have to cut non-defense federal spending in 2016 by roughly $500 billion.

Romney doesn’t deny this. On the contrary, he’s been refreshingly honest on this subject. In the Washington D.C., speech where he laid out his budget vision, he said “we’ll need to find almost $500 billion in savings a year in 2016.” But Romney has not given many details on what that would entail. (Nor did his campaign respond to questions about this from TNR.) Perhaps that's because the impact of these cuts would scare the bejeezus out of some people.

Or perhaps it's because Romney doesn't intend to follow through on his cuts. But some even rough idea of where he would cut is surely worth knowing.