[In the absence of debt ceiling increase] federal spending would instantly have to be reduced by about $100bn per month. By the end of 2011 federal spending would be about $500 bn lower for the year than it would have been otherwise.
I’ve made this point before, but for numbers that large, anyone who wants to pretend to have some understanding about the economy has to think about macroeconomic effects. In particular, spending cuts of that size would reduce the US’s 2011 GDP by multiple percentage points. The Q3 and Q4 GDP growth rates wold probably be on the order of between -5% and -10%. Recall that during the recession of 2008-09, GDP only fell by about 4% in total. The unemployment rate would be likely to rise by several percentage points from its current level of 9.2%, to perhaps 15% or more of the US population. Recall that at its worst, the unemployment rate during the Great Recession only reached 10%.
So when you read someone blithely writing that the federal government will not default in the absence of a debt ceiling deal, and instead will merely have to trim excess spending, remember that what they’re really advocating is a new and deliberately caused Great Depression.