The bulk of that change occurred in CBO’s estimates of revenues: The agency has reduced its projection of total revenues by $1.6 trillion, largely because of changes in the economic outlook. A decrease of $0.6 trillion in projected outlays through 2023 partially offset that change.
2) And we're not even meeting that reduced potential. The CBO also thinks it will be a long time before the country gets back to full employment. The unemployment rate isn't expected to fall below 6 percent until late 2017.
For example, if the growth of real GDP and taxable income was 0.1 percentage point higher or lower per year than in CBO’s baseline projections, revenues would be roughly $270 billion higher or lower over the 2015–2024 period.