RBC modeli in mentalna zloraba

Noah Smith branjenje z Nobelovo nagrado ovenčanih real business cycles (RBC) modelov, ki zaradi mikrofundiranosti ne dopuščajo, da bi lahko kriza nastala endogeno (povzročena z notranjimi silami v gospodarstvu), pač pa vedno pride od zunaj kot eksogen šok – kot šok v produktivnosti, naftni šok ali šok iz Marsa, označuje kot gaslighting. Torej kot mentalno zlorabo z manipulacijo informacij, ob kateri na koncu zlorabljenec podvomi v svoje lastno duševno zdravje. Navdušenci nad RBC modeli namreč že tri desetletja poudarjajo, kako je to superioren ekonomski model, pri čemer pa jim stalno nagajajo podatki, ki kljub zvijanju in lomljenju rok nikakor nočejo slediti implikacijam modela.

The basic 1982 Nobel-winning RBC model – a complete-markets, representative-agent theory of business cycles where productivity shocks, leisure preference shocks, and/or government policy distortions drive business cycles – has never been very good at matching the data. This didn’t take long to figure out – a lot of its implications seemed fishy right from the start and required patching. Simple patches, like news shocks, didn’t really improve the fit that much. The model isn’t very robust to small frictions, either. And one of the main data techniques used in RBC models – the Hodrick-Prescott filter – has been mathematically shown to be very dodgy. Furthermore, the Nobel-winning empirical work of Chris Sims showed that the main policy implication of RBC – that monetary policy can’t be used to stabilize the real economy – doesn’t hold up.

Now, that doesn’t mean RBC is a total failure. There are some cases, as with large oil discoveries, when it sort of looks like it’s describing what’s going on. And very advanced modifications of basic RBC – labor search models, heterogeneous-agent models, network models, etc. – offer some hope that models that rely on TFP shocks as the main stochastic driver of aggregate volatility may eventually fit the macro data.

But that’s not enough for RBC fans! The idea of RBC as one potentially small ingredient of an eventual useful theory of the business cycle is not enough. RBC fans maintain that RBC is the basic workhorse business cycle model.

For example, just last year, Ed Prescott and Ellen McGrattan released a paper claiming that if you just patch basic RBC up with one additional type of capital, it fits the data just fine. As if this were the only empirical problem with RBC, and as if this new type of capital has empirical support!

This strikes me as a form of gaslighting – RBC fans just blithely repeat, again and again, that the 1982 RBC model was a great empirical success, that it is now the standard model, and that any flaws are easily and simply patched up. They do this without engaging with or even acknowledging the bulk of evidence from the 1990s and early 2000s showing numerous data holes and troubling implications for the model. They don’t argue, they just bypass. Eventually, like the victims of gaslighting, skeptical readers may begin to wonder if maybe their reasoning capacity is broken.

Gaslighting or gas-lighting is a form of mental abuse in which information is twisted or spun, selectively omitted to favor the abuser, or false information is presented with the intent of making victims doubt their own memory, perception, and sanity.

Vir: Noah Smith

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