Martin Wolf has a nice post explaining the financial crisis using sector financial balances. He rightly attributes this way of looking at things to Wynn Godley. It goes way back – I remember using them as a cross-check on forecasts in the UK Treasury in the 1970s, but it was probably Godley’s influence that helped that happen too. They are not a substitute for thinking about macroeconomic behaviour, but they can often be a very useful check on whether your thoughts (or forecasts) make sense.
Take the example of a balanced budget temporary increase in government spending, which I used recently as a challenge to heterodox economists to come up with an alternative analysis that did not use either representative agents or rational expectations. (I’ve had plenty of responses telling me of all the defects of rational expectations, but no one has as yet given me an alternative account of the impact of this particular policy measure. As Godley is respected among heterodox economists, I thought maybe retelling my analysis using sector balances might help.)
The policy itself does not directly change the government sector’s financial balance (by definition). Theory tells us that consumers will smooth the impact of temporarily higher taxes, so their sector will move into deficit. But if we were foolish enough to think the story stopped there, thinking about financial balances tells us that has to be wrong. Consumers are in deficit, and no sector has moved into surplus. Keynesian theory then tells us what happens to put things right: output and incomes increase until the point that the consumer sector is no longer in deficit. If you think about it (and given consumption would always fall by less than post-tax income because of smoothing), this has to be the point at which income has increased by an amount equal to the tax increase i.e. a balanced budget multiplier of one. We could talk about this as a dynamic multiplier process, or we could talk about rational consumers working this out, and so not bothering to reduce their consumption in the first place.
As Martin Wolf and others have pointed out many times, thinking about financial balances also tells us the foolishness of cutting government deficits when the private sector has moved into surplus to restore their asset/liability position. In a global economy, if governments are successful in cutting deficits then the private sector surplus has to diminish. That makes the idea that nothing will happen to output as a result of deficit reduction rather improbable. With interest rates stuck at zero, real interest rates cannot move to persuade the private sector that they no longer need to correct their financial position. So the only possibility left is that output falls until they no longer want to do so. (Because of consumption smoothing higher short term income would imply a rising, not falling, private sector surplus.)
Looking at sector balances are not a substitute for thinking about behaviour, but they can and should demand that we are able to tell stories about them that make sense. Where I think criticism of the mainstream macroeconomic profession is correct is that there were not enough people telling convincing stories about why the household sector balance was evolving the way it did over the two decades before the recession. (I talk more about this here.) What was I doing? The answer is writing papers looking at the impact of fiscal policy in DSGE models, and not looking at this kind of data at all. In that sense I was definitely part of the problem, although it did kind of come in useful later on.