Economic models

From Aaron Schiff:

A model should not be judged solely by its assumptions (although highly dubious assumptions are not a good thing). Rather we should focus on the model’s ability to teach us something, and its ability to explain the economics of something in a plausible way.

To summarise, a model does:

  • Highlight the incentives or tradeoffs that are relevant in a particular economic situation.
  • Generate predictions about the behaviour of economic agents in response to controlled changes in conditions.

I took this from a good post by Aaron Schiff.  I agree with it.

Note that the purpose of economic models isn’t prediction (as we have been discussing) – but we do want a testable hypothesis, in order to make our models scientifically valid.  So the model MUST be testable, but this is not a sufficient condition on models.

Furthermore, predicitive accuracy is not part of testability – as the difference could stem from a change from one of our ceteris paribus (CP) assumptions.

The goal is explanation and description.  And trust me the grey line between prediction and testablility is problematic.  But for the purpose of discussing economic models, the fact that our CP assumptions are the things that break unexpectedly does not invalidate the usefulness or purpose of economic models.

Note:  I will stop writing on this soon and go back to NZ economics.  For me this stuff is interesting, and I like to have a record of where my head is at.

Attacks from the left and the right on economics

One thing I have noticed in my time is that people on the political left and right both attack “mainstream economics” with abandon.  This is good, as a discipline has to be able to explain itself widely and be willing to face criticism.

However, it is one of the elements of these attacks that interests me here.  Namely, how each side of the political spectrum attacks the “focus” of economics, or the framing – specifically in terms of the market and government.  Here is my oversimplified understanding of this element:

  • Left:  Economists are focused on markets.  They start from a place where markets are perfect, and markets provide the best outcomes and work from there – therefore they have a pro-market bias.
  • Right:  Economists focus on markets and resource allocation.  The focus on markets makes them dwell on policies that solve “market failures” rather than paying attention to the possibility of government failures!  As a result they have a bias to push policies that are anti-market.  Furthermore, by discussing the allocation of resources they drive the feeling that the economy can be controlled – which also leads to a bias towards government involvement.

I find both of these attacks suffer from the same problem, they avoid trying to understand why economists use the counter-factual they do, and the way economic analysis stems from it.

In itself, economics is not about giving policy prescriptions, it is about “trying” to “objectively” describe and explain an economic situation.  We find the elements of a market (which is the voluntary trade relevant to the issue at hand), and try to model them.  When then describe a “perfect counterfactual” and look at how these elements cause outcomes to differ.  We then do nothing.

In this case, the purpose of our counterfactual is to give some idea about how a more “realistic” outcome compares to an “ideal” outcome.  We do not say that the ideal outcome is possible, we do not say that any policies could move us towards the ideal outcome, and as strict economists we do not place hefty welfare judgments on the relative outcomes.  The counterfactual is solely there to allow us to describe, in some sense, how the elements in the model impact on the outcome – it helps us to describe.

The next stage is more “subjective” (I am putting commas around objective and subjective as even the “objective” analysis involves a number of subjective assumptions – but I digress), and it is not in the realm of economics per see.  Economists often move on to the policy analysis stage, but it is an additional element, that requires different skills than those that are central to economics.

The biases the left and right discuss tend from their view of the value judgments made by analysts at this stage of analysis – they are not relevant in a discussion about economists.  As a result, although the left and right often like to tarnish all economists with the same brush this is just not the case – economics is not the issues they disagree with here, but the value judgments made in the application of economic models.  The critique is of analysts they do not agree with, not the discipline as a whole.

Of course, I do not expect individuals with a political mind to ever properly accept or represent this significant difference – as there is too much satisfaction and political capital associated with attacking all economists 😀

Data and prediction

Via Scott Sumner we saw the following article that mentions economic data and economic predictions.  The statements that stood out to me were:

(Economic) predictions are, of course, the bread and butter of economic institutions. But can we believe them?

In recent years, some economists have begun to express doubts over predictions made from huge volumes of data, but they are in the minority. Most embrace the idea that more measurements mean better predictive abilities.

Hold up.

For one, as we have mentioned prediction is not the central element of what economists do – and even when they do predict the goal of such prediction is to give some view regarding risks and movements, not direct figures (it is more ordinal than cardinal in some sense).

Secondly, ever since the Lucas critique economists have been very nervous about predictions from large amounts of data without theory – I would say that the majority of economists doubt the usefulness of econometric models relying solely on huge amounts of data.

Economists would like data with less measurement error, that is closer to representing the true economic variables we discuss in theory – we aren’t looking for an infinite number of measures we can stick together to find a result.  An economist that doesn’t use theory to inform their discussions of the economic outlook, but uses lots of data, isn’t an economist – that is all.

Technology: Dystopia or utopia?

Nick Rowe has a great post on technology and labour.  Fundamentally, it states that, one day, increases technology and improving capital will replace labour, destroying demand for labour.  I was discussing a similar issue with Linuxlover on Twitter (and who blogs here).

Both men seemed to imply that such a situation could be a bad thing.  Linux lover told me of the “legion of unemployed”, while Nick mentioned a book that states:

It describes life in the near-future when technology and machines have destroyed the demand for nearly all human labour, except for the labour of a small, highly-educated minority. The vast majority of the population would be unemployed, but for government make-work projects

However, I am not afraid of such an occurrence per see – in fact I am excited.  Why?  What is wrong with me?

Read more

Incentive problems in econ?

So there has been discussion on incentive problems in economics here before (here, here, and here).  However, now there seems to be a little bit of hard empirical evidence indicating that there is a problem.

It seems that 51% of graduate students at the top 15 US universities think that knowledge of the actual economy was “unimportant” for doing a degree in economics.  These weren’t people saying “a little important” or “I’m not sure”, these are just the ones saying “it does not matter at all”.

Now, if the best graduate students do not believe that the actual economy matters for economics that suggests to me that there is a major incentive problem – the same sort of one that Rauparaha tried to convince me about so long ago

Wages and recovery: A note

There seems to be some hatred for the idea that if nominal wages were more flexible unemployment would not rise as high (here, here, and here).

However, I am a fan of the flexibility argument – and not just because my mind struggles to get outside of partial equilibrium 😉

When I view wage flexibility I think about it in THREE ways that would lead to an improvement in outcomes – in so far as they would reduce the “market failure” that leads to a “surplus of labour”.  These are both RELATIVE PRICE arguments:

  1. Wages relative to substitute inputs:  Wages need to be able to adjust more quickly than other inputs.  If this is the case then employers would cut back on other inputs ahead of labour.  Given that there is both substitutability and complementarity in inputs this is a difficult issue – but nonetheless.
  2. Wages relative to goods:  Wages need to be able to adjust more quickly than goods prices.  That way real wages will decline, making labour relatively cheaper.
  3. Relative wages:  This is the big one for me.  Often during a recession there may need to be a reallocation of labour resources, or there may be uneven shifts in demand for types of labour.  If relative wages can adjust then we ensure that the cost (in terms of climbing unemployment and general economic inefficiency) can be minimised.