Nick Rowe tiene un interesante y provocador post sobre los modelos Keynesianos, haciendo hincapié en criticar a los nuevo keynesianos (que no son los neo). El énfasis en el tinkerbell effect es genial. Les recomiendo leer también los comentarios.
Este post me hizo recordar a un profesor visitante dedicado a la economía monetaria que dijo: “¿que es ser keynesiano?, nunca estudie eso”.
Suppose that, due to past monetary mismanagement, the economy is currently in recession, and is expected to be in recession next period as well. What should the central bank do?
In an Old Keynesian model, the answer is simple. Cut the real interest rate, so consumption demand increases, and the economy moves down along the IS curve till it gets to “full employment” (or whatever the central banker thinks is full employment, the natural rate, the NAIRU, or whatever).
In a New Keynesian model, the answer is not simple. In fact, there isn’t a well-defined answer to this question. A cut in the real interest rate might cause an increased level of consumption today, and no change in planned future consumption. That will help the economy escape the recession. But it might also cause a cut in planned future consumption, with no change in consumption today. That will not help the economy escape the recession.
It doesn’t help to assume the cut in the real interest rate is expected to be permanent. A permanent 1% cut in the interest rate might just cause people to decrease planned future consumption by (say) 2% every year from the year before, so that planned consumption asymptotically approaches zero. That will simply cause people to expect the economy to slide progressively deeper into recession.
There is only one time-path of real interest rates that is compatible with a 100% full employment time-path in a new Keynesian model. But that exact same time-path of real interest rates is also compatible with a time-path where output is only 90% of full employment, or 80%, or 70%, or any time-path of output whatsoever, as long as the ratios between one year’s output and the next year’s output are the same as in the 100% path.
How do New Keynesian macroeconomists avoid the problems posed by this question? They avoid asking the question. They simply assume that at some time in the future the economy will be at full employment, where output is determined by the supply-side, and that people’s currently planned future consumption for that date equals full employment output. With current plans for future consumption pinned down exogenously at some future time, they can solve the model backwards to find the path of real interest rates that will keep the economy at full employment up till that time.