Views on the minimum wage show economics to be an inexact science

.The hallmark of a science is not just having refutable hypotheses, but also changing its view when data shows the theory is wrong. Economics is often accused of not being a science. A good test case to see if that is true is the minimum wage. Basic economic theory suggests if you fix wages at above their level in the market, employment will fall as less workers are employed. However a number of empirical studies, the most well known of which was written by Card and Krueger in 1994, have suggested that employment shows no noticeable decline when a minimum wage is imposed or modestly increased. My reading is that the most convincing studies do show this result, but not all do, so the picture is not completely clear.

This illustrates a problem for economics (and all social sciences) that outsides often fail to appreciate. Measurements and econometric studies are often not conclusive, and even in the case of austerity you can find one or two empirical studies which says something different to all the rest. As a result, it is more difficult to use data to show a hypothesis is conclusively wrong in the way the natural sciences can. My own view is that the balance of studies clearly shows a modest minimum wage has no noticeable impact on employment, but others would disagree.

Here is a question from the IGM survey.of around 50 top US economists on the minimum wage

Academic economists appear evenly divided, and few hold a strong opinion on the issue. A similar survey of UK economists, asked about the 2016 increase in the minimum wage, was also divided but lent more towards no effect. In contrast, most German economists appear to have been opposed to the recent introduction of a minimum wage.

If you were cynical you might say that all this shows is that the views of economists just reflect their political opinions, and I would indeed expect there would be a clear correlation to support that with the minimum wage. However when either theory or evidence are pretty clear, economists do not divide by political opinion. The same survey in 2012 and 2014 showed economists largely agreeing that the Obama stimulus reduced unemployment and was beneficial, even though the political right was strongly opposed to it. The reason is that economic theory and nearly all evidence shows that fiscal expansion when interest rates are stuck at their lower bound is expansionary.

Equally standard microeconomic theory is just as clear that the minimum wage will reduce employment, and I suspect that had this survey been done in the early 1990s most academics would have agreed with this, whatever their political persuasion. What has changed is the evidence. This example clearly shows a good number of academics responding to empirical results that conflict with standard theory.

Furthermore some economists have done what good scientists should do and produced new theories which can explain the empirical results that the minimum wage does not reduce employment. In that sense economists have been behaving as a science should. But because there are some contrary studies, that allows two things that distinguish economics from physical sciences. The first thing is a temptation to hold on to basic theory even though the balance of evidence is against it, something that is not totally absent in the physical science either (Kuhn, Lakatos etc). The second is to allow ideological influences to help decide what should be a scientific judgement. These are the senses in which economics is an inexact science.

For those interested in economic methodology, and excellent place to start is here, the title of which I am abusing in this post. However it is also worth reading this for sources on the new 'empirical turn' in economics. On the impact of ideology on economics a great place to start is this thread from Beatrice Cherrier. On the introduction and history of the minimum wage in the UK, including initial political resistance to it, see here.

Economics is an inexact science

When I wrote about why the BBC should treat a clear consensus in economics the same way as it now treated climate science, I got a number of comments about why economics is not a science. A common theme was that economics couldn’t prove theories ‘beyond doubt’ the same way as the hard sciences could. A more sophisticated version of this complaint is that most economic theories cannot be disproved in the same way that Popper thought scientific theories could be disproved.

All this ignores a key feature of any social science, which is their inexact nature. Instead we have accumulations of evidence that confirm the applicability of some theories and reject the applicability of others. Economists’ views about what models are applicable change as this evidence accumulates.

A good example involves the minimum wage, as Noah Smith suggests. The basic economic model suggested even a modest minimum wage should significantly reduce employment, but economists discovered that the evidence did not show this. As this evidence accumulated, alternative theories and models (monopsony and search) were thought to be more relevant. It is this response to evidence that makes economics a science.

Jo Michell writes “The scientific method of forming a hypothesis and then testing that hypothesis against reality can never be the final arbiter of knowledge, as it can in the physical sciences.” He is right that no single experiment or regression can kill a theory, but wrong that the accumulation of evidence is not the final arbiter, because no other arbiter is available. He links to a post by Noah Smith which talks about the failures of forecasting. But as that post makes clear, this is not about data rejecting models, but the inability of models to predict the future. We would never dream of condemning medics because they cannot predict the exact time of our death, still less suggest that this failure indicates they are not doing science.

Of course economics involves cases where economists appear too reluctant to give up their favoured models. You can find similar stories in the hard sciences. There will be more such stories in economics because the inexact nature of economics makes it easier to discount any single piece of evidence. What I cannot understand is what leads someone like Russ Roberts to argue against the use of evidence, and instead that “economics is primarily a way of organizing one’s thinking”. Astrology is also a way of organising one’s thinking, but it fails because evidence does not back it up.

That comparison is slightly unfair, because while the theory behind astrology is obviously implausible, the basic principles of microeconomics are not. In a class on economic methodology I once drew a huge tree that showed how most of economics could be derived from principles of rational choice. But go beyond the basics, and add in complications involving information and transactions costs (to name but two) and you very quickly derive competing models. There is no single model that comes from thinking like an economist, so for that reason alone we need data to tell us which models are more applicable.

So thinking like an economist does not tell me at what point raising the minimum wage will reduce employment. But why would anyone want to keep their models from being proved relevant or otherwise by data? The only reason I can think of is that some models give answers that are ideologically convenient. Of course allowing data to establish the relevance of some models over others does not make economics ideology proof. For example people can always select the one study that suggests that fiscal policy does not influence output and ignore the hundreds that show otherwise. That is why the accumulation of evidence, which includes its replicability, is so important. If you think economics has problems in that respect, have a look at psychology.

This is why economists views about the long term impact of Brexit should be treated as knowledge rather than just an opinion. Here knowledge is shorthand for the accumulation of evidence consistent with plausible theory. Sometimes the theories are common sense, like making trade more difficult will reduce trade. Estimates of the size of trade reduction based on evidence are uncertain, but they are better than estimates based on wishful thinking. Empirical gravity equations consistently show that geography still matters a lot in determining how much is traded. Finally there is clear evidence that trade is positively associated with productivity growth. To say that all this has no more worth than some politicians opinion is ultimately to degrade evidence and the science which interprets it.