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Friday, July 18, 2014

'Further Thoughts on Phillips Curves'

Simon Wren-Lewis:

Further thoughts on Phillips curves: In a post from a few days ago I looked at some recent evidence on Phillips curves, treating the Great Recession as a test case. I cast the discussion as a debate between rational and adaptive expectations. Neither is likely to be 100% right of course, but I suggested the evidence implied rational expectations were more right than adaptive. In this post I want to relate this to some other people’s work and discussion. (See also this post from Mark Thoma.) ...
The first issue is why look at just half a dozen years, in only a few countries. As I noted in the original post, when looking at CPI inflation there are many short term factors that may mislead. Another reason for excluding European countries which I did not mention is the impact of austerity driven higher VAT rates (and other similar taxes or administered prices), nicely documented by Klitgaard and Peck. Surely all this ‘noise’ is an excellent reason to look over a much longer time horizon?
One answer is given in this recent JEL paper by Mavroeidis, Plagborg-Møller and Stock. As Plagborg-Moller notes in an email to Mark Thoma: “Our meta-analysis finds that essentially any desired parameter estimates can be generated by some reasonable-sounding specification. That is, estimation of the NKPC is subject to enormous specification uncertainty. This is consistent with the range of estimates reported in the literature….traditional aggregate time series analysis is just not very informative about the nature of inflation dynamics.” This had been my reading based on work I’d seen.
This is often going to be the case with time series econometrics, particularly when key variables appear in the form of expectations. Faced with this, what economists often look for is some decisive and hopefully large event, where all the issues involving specification uncertainty can be sidelined or become second order. The Great Recession, for countries that did not suffer a second recession, might be just such an event. In earlier, milder recessions it was also much less clear what the monetary authority’s inflation target was (if it had one at all), and how credible it was. ...

I certainly agree with the claim that a "decisive and hopefully large event" is needed to empirically test econometric models since I've made the same point many times in the past. For example, "...the ability to choose one model over the other is not quite as hopeless as I’ve implied. New data and recent events like the Great Recession push these models into unchartered territory and provide a way to assess which model provides better predictions. However, because of our reliance on historical data this is a slow process – we have to wait for data to accumulate – and there’s no guarantee that once we are finally able to pit one model against the other we will be able to crown a winner. Both models could fail..."

Anyway...he goes on to discuss "How does what I did relate to recent discussions by Paul Krugman?," and concludes with:

My interpretation suggests that the New Keynesian Phillips curve is a more sensible place to start from than the adaptive expectations Friedman/Phelps version. As this is the view implicitly taken by most mainstream academic macroeconomics, but using a methodology that does not ensure congruence with the data, I think it is useful to point out when the mainstream does have empirical support. ...

    Posted by on Friday, July 18, 2014 at 08:21 AM in Econometrics, Economics, Macroeconomics | Permalink  Comments (9)

          


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