How much money does the capital gains tax bring in?
Here's a graph of capital gains tax revenue, along side the federal deficit for reference
What stands out to me is that the deficit is a lot more volatile (and almost always larger) than cap gains revenue. The relative stability of capital gains revenue is not exactly what I'd expect considering the erosion over time of the tax base due to the growing number of tax-privileged vehicles like 401k, IRA, HSA, 529 and others. In the most recent year of data, 2014, cap gains revenue amounted 25.4 percent of the deficit. Essentially, selling bonds is four times as big a source of funds for the federal government as taxing capital gains. Here's what that ratio looks like over time:
