David C. Saha z Bruegla je pripravil dober povzetek debate zadnjih nekaj tednov o veljavnosti teorije racionalnih pričakovanj v ekonomiji.

Moj zelo kratek povzetek debate: ni konsenza med ekonomisti, se pa večinsko mnenje (sodelujočih v debati) nagiba v smer, da se po eni strani ljudje običajno odločajo na podlagi sedanjih informacij oziroma preteklosti (t.j. na podlagi adaptivnih oziroma naivnih pričakovanj) in se izogibajo kompleksnim optimizacijskim preračunom v glavi, ki jih zahteva predpostavka racionalnih pričakovanj, po drugi strani pa so pred njimi odločitve, ki zahtevajo bolj celovit razmislek. Ali drugače rečeno, kot pravi Chris Dillow, michiganski podatki o gibanju dejanske in napovedane (anketne) inflacije dajejo slutiti, da se v normalnih časih inflacijska pričakovanja oblikujejo na podlagi preprostega “backward looking” pravila palca, medtem ko v izjemnih časih ljudje pravilo palca zamenjajo za bolj kompleksne miselne procese.

Spodaj pa še nekaj zanimivih mnenj:

Mark Thoma takes a measured view of rational expectations. On the one hand, it would be foolish to assume people didn’t use new information and purely extrapolated from past trends. Who would assume a trend will continue when there is good information saying otherwise? And one should think that people will react to announced changes in policies. On the other hand, it is quite a stretch to assume that people fully understand the policy rules used as well as how they will impact the economy.  Simplifications, rules of thumb or hard-wiring may explain quite a bit – e.g. why we can catch a ball in flight without solving complicated differential equations – and the correction of individual errors on markets may explain even something more, but it is to be doubted that it extends to fully approximating the functioning of complex markets. Rational expectations may be a good benchmark, just like the assumption of a perfect vacuum in physics, and may approximately hold in some contexts such as simple games and financial markets.  However, it would be a mistake to assume they apply universally.

Nick Rowe writes that one should expect people to use rules of thumb in reality. This is a rational strategy for individuals as long as the world is well approximated by the rule used. For any naive way of forming expectations, there exists a world in which that naive way of forming expectations would be rational. In a world where the price level followed a random walk – something like the Gold Standard world – the naive expectation of 0% inflation is rational. In a world where the price level followed a random walk plus 2% drift, roughly a 2% inflation target world, the naive expectation of 2% inflation would be rational. And if the inflation rate followed a random walk, the naive expectation that next period’s inflation rate would be the same as last period’s inflation rate would be rational. It’s when the world changes that things get tricky.  The naive expectations that were rational in the old world aren’t rational in the new world. This comes down to an argument for small c-conservatism in monetary policy rules and elsewhere in order to keep expectations rational for longer than they otherwise would be.

Robert Waldmann points out that the Michigan Survey (inflation expectations of ordinary people) shows that inflation expectations are closely correlated to current CPI inflation – except when large external shocks such as oil price shocks occur. And in recent years, survey forecast inflation is persistently higher than actual inflation – while people’s estimates of current inflation also exceed actual figures. This does not seem in tune with rational expectations either and rather point towards backwards-looking expectation formation.

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Chris Dillow  points out that in the data, expected inflation and perceived inflation are strongly correlated. While this may be consistent with some rational expectations, it is also largely consistent with a simple rule of thumb: expect inflation to be what it is now, but adjust down if inflation is unusually high, and up if it’s unusually low. However, this rule of thumb does not seem to hold for exceptional circumstances. During the recession, inflation expectations were lower than those this rule of thumb would generate. Maybe, it is reasonable to suspect that inflation expectations are indeed formed by backward looking simple rules of thumb in normal times – but in exceptional times, people abandon rules of thumb for more complex processes as the costs of being wrong increase.

Več preberite na David C. Saha, Bruegel