Sonntag, 5. Juli 2015

Nichtlineare Makromodelle mit endogenen Zyklen

Beaudry et al. (2015) nehmen in einem neuen Beitrag die (alte) Idee auf, dass Makromodelle endogene Wirtschaftszyklen generieren können sollten, bzw. werfen die Frage wieder auf, ob das nicht plausibler sei als die auch lokal stabilen linearen Modelle, die in den vergangenen Dekaden en vouge waren.

Auf der VOX-Seite gibt es eine verständliche Zusammenfassung ihres sehr technischen Papiers:
"There are two polar views about the functioning of a market economy.
  • On the one hand, there is the view that such a system is inherently stable, with market forces tending to direct the economy to a smooth growth path.
According to such a belief, most of the fluctuations in the macroeconomy result from either individually optimal adjustments to changes in the environment or from improper government interventions. In such a case, the role of macroeconomic policy should be to do no harm; if policymakers hold back from actively influencing the economy, market forces would take care of the rest and foster desirable outcomes.
  • On the other hand, there is the view that the market economy is inherently unstable, and that left to itself it will repeatedly go through periods of socially costly booms and busts, with recurrent periods of sustained high levels of unemployment.
According to this view, macroeconomic policy is needed to help stabilise an unruly system. 
   
Most modern macroeconomic models, such as those used by large central banks and governments, are somewhere in between these two extremes. However, they are by design much closer to the first view than the second, and this is generally not fully appreciated. In fact, most commonly used macroeconomic models have the feature that, in the absence of outside disturbances, the economy is expected to converge to a stable path. In this sense, these models are based on the premise that a decentralised economy is a stable system and that market forces, in of themselves, do not tend to produce boom and busts. The only reason why we see economic cycles in mainstream macroeconomic models is due to outside forces that perturb an otherwise stable system. We can call such a framework the stable-with-shocks view of the macroeconomy. [...]

But why should we care if the macroeconomy is locally unstable versus if it is locally stable? Society’s understanding of how the economy functions, especially what creates business cycles, greatly affects how we design stabilisation policy. 

In the current dominant paradigm, there is a tendency to see monetary policy as the central tool for mitigating the business cycle. This view makes sense if excessive macroeconomic fluctuations reflect mainly the slow adjustment of wages and prices to outside disturbances within an otherwise stable system. 

However, if the system is inherently unstable and exhibits forces that favour recurrent booms and busts of about seven to ten years intervals, then it is much less likely that monetary policy is the right tool for addressing macroeconomic fluctuations. Instead, in such a case we are likely to need policies aimed at changing the incentives that lead household to bunch their purchasing behaviour in the first place."

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