The very large budget deficit in 2009 is attributed to a combination of discretionary policy and:

1. Deficits can grow without any new law being passed. 2. Discretionary fiscal policy requires a new law changing tax or spending levels. 3. Other budget changes happen automatically as the economy moves. 4. A combination of automatic stabilizers and discretionary fiscal policy produced the deficit. 5. That combination produced the very large budget deficit in 2009. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 16 'Government Budgets and Fiscal Policy'_