Jan Hatzius of Goldman Sachs has a new note (no link) responding to claims that government support for the economy is postponing the necessary adjustment. He doesn’t think much of that argument; neither do I. But one passage in particular caught my eye:

The private sector financial balance—defined as the difference between private saving and private

investment, or equivalently between private income and private spending—has risen from -3.6% of GDP in the 2006Q3 to +5.6% in 2009Q1. This 8.2% of GDP adjustment is already by far the biggest in postwar history and is in fact bigger than the increase seen in the early 1930s.

That’s an interesting way to think about what has happened — and it also suggests a startling conclusion: namely, government deficits, mainly the result of automatic stabilizers rather than discretionary policy, are the only thing that has saved us from a second Great Depression.

The following figure makes the argument:

Here I show the private sector surplus and the public sector deficit, both as functions of GDP; the private sector line is upward-sloping because higher GDP means higher income and more savings, the public-sector line is downward-sloping because higher GDP means higher revenues. In equilibrium the private surplus equals the government deficit (not strictly true for any one country if you add in international capital flows, but think of this as a picture for the world economy). To make the figure cleaner I’ve shown an initial position of balance in both sectors, but this isn’t important.

What we’ve had is a sharp increase in the desired private surplus at any given level of GDP, due to a combination of higher personal saving and reduced investment demand. This is shown as an upward shift in the private-surplus curve.

In the 1930s the public sector was very small. As a result, GDP basically had to shrink enough to keep the private-sector surplus equal to zero; hence the fall in GDP labeled “Great Depression”.

This time around, the fall in GDP didn’t have to be as large, because falling GDP led to rising deficits, which absorbed some of the rise in the private surplus. Hence the smaller fall in GDP labeled “Great Recession.”

What Hatzius is saying is that the initial shock — the surge in desired private surplus — was if anything larger this time than it was in the 1930s. This says that absent the absorbing role of budget deficits, we would have had a full Great Depression experience. What we’re actually having is awful, but not that awful — and it’s all because of the rise in deficits. Deficits, in other words, saved the world.