Macroeconomics tells you to (temporarily) raise, not cut, government spending when we have a recession caused by deficient demand and interest rates are at their lower bound. That is the claim that some of us make. Others say we are being far too sure of ourselves and our subject, in part because there exist models where this is not true. As a result, we should not loudly complain when politicians do not follow this advice. A bit more humility please.
If you think we should have more humility, imagine the following. The UK or US government tomorrow abolishes their independent central bank, and immediately raises rates to 5%, saying it was about time savers had a better deal. Well macroeconomists generally think that independent central banks are a good idea, and we nearly all believe that raising interest rates when inflation is below target and unemployment is high is crazy. But wait a minute. There are models that suggest keeping interest rates low is causing low inflation, and that raising rates could stimulate the economy - I discuss one here. So perhaps we should not be critical of a government that did this. We should be humble, and leave the politicians to do as they please while we get on with our research. Let us make sure we are absolutely sure before shouting too loud.
Why is that wrong? Two reasons. First, the existence of a model that says higher interest rates could stimulate the economy is not in itself evidence that it might. In an interesting paper, Paul Pfleiderer talks about Chameleon models. He defines a chameleon model as “built on assumptions with dubious connections to the real world but nevertheless has conclusions that are uncritically (or not critically enough) applied to understanding our economy.” The model that I discussed where higher rates could stimulate the economy assumes (among other things) agents believe the inflation target is negative, and that raising rates will show them they are wrong. Possible, but highly improbable.
Second, economic policy always takes place in an uncertain environment. Raising interest rates might have reduced inflation in the past, but maybe this time is different? If we wait until we are all absolutely sure about the impact of a policy change, we will wait forever. However, if we are more than 90% certain that raising interest rates, or cutting government spending, will make the recession worse, we should say so. If politicians ignore this advice, we should make sure everyone knows. This is no intellectual game - people’s welfare is at stake.