Home > Uncategorized > DSGE models — unparalleled and spectacular failures

DSGE models — unparalleled and spectacular failures

from Lars Syll

The unsellability of DSGE models — private-sector firms do not pay lots of money to use DSGE models — is one strong argument against DSGE.

But it is not the most damning critique of it.

To me the most damning critiques that can be levelled against DSGE models are the following two:

DSGE models are unable to explain involuntary unemployment

In the basic DSGE models the labour market is always cleared – responding to a changing interest rate, expected lifetime incomes, or real wages, the representative agent maximizes the utility function by varying her labour supply, money holding and consumption over time. Most importantly – if the real wage somehow deviates from its ‘equilibrium value,’ the representative agent adjust her labour supply, so that when the real wage is higher than its ‘equilibrium value,’ labour supply is increased, and when the real wage is below its ‘equilibrium value,’ labour supply is decreased.

In this model world, unemployment is always an optimal choice to changes in the labour market conditions. Hence, unemployment is totally voluntary. To be unemployed is something one optimally chooses to be.

The D WordAlthough this picture of unemployment as a kind of self-chosen optimality, strikes most people as utterly ridiculous, there are also, unfortunately, a lot of neoclassical economists out there who still think that price and wage rigidities are the prime movers behind unemployment. DSGE models basically explain variations in employment (and a fortiorioutput) with assuming nominal wages being more flexible than prices – disregarding the lack of empirical evidence for this rather counterintuitive assumption.  

Lowering nominal wages would not clear the labour market. Lowering wages – and possibly prices – could, perhaps, lower interest rates and increase investment. It would be much easier to achieve that effect by increasing the money supply. In any case, wage reductions were not seen as a general substitute for an expansionary monetary or fiscal policy. And even if potentially positive impacts of lowering wages exist, there are also more heavily weighing negative impacts – management-union relations deteriorating, expectations of on-going lowering of wages causing delay of investments, debt deflation et cetera.

The classical proposition that lowering wages would lower unemployment and ultimately take economies out of depressions, was ill-founded and basically wrong. Flexible wages would probably only make things worse by leading to erratic price-fluctuations. The basic explanation for unemployment is insufficient aggregate demand, and that is mostly determined outside the labour market.

Obviously, it’s rather embarrassing that the kind of DSGE models ‘modern’ macroeconomists use cannot incorporate such a basic fact of reality as involuntary unemployment. Of course, working with representative agent models, this should come as no surprise. The kind of unemployment that occurs is voluntary since it is only adjustments of the hours of work that these optimizing agents make to maximize their utility.

In DSGE models increases in government spending leads to a drop in private consumption

In the most basic mainstream proto-DSGE models one often assumes that governments finance current expenditures with current tax revenues.  This will have a negative income effect on the households, leading — rather counterintuitively — to a drop in private consumption although both employment an production expands. This mechanism also holds when the (in)famous Ricardian equivalence is added to the models.

Ricardian equivalence basically means that financing government expenditures through taxes or debts is equivalent since debt financing must be repaid with interest, and agents — equipped with rational expectations — would only increase savings in order to be able to pay the higher taxes in the future, thus leaving total expenditures unchanged.

Why?

In the standard neoclassical consumption model — used in DSGE macroeconomic modelling — people are basically portrayed as treating time as a dichotomous phenomenon – today and the future — when contemplating making decisions and acting. How much should one consume today and how much in the future? Facing an intertemporal budget constraint of the form

ct + cf/(1+r) = ft + yt + yf/(1+r),

where ct is consumption today, cf is consumption in the future, ft is holdings of financial assets today, yt is labour incomes today, yf is labour incomes in the future, and r is the real interest rate, and having a lifetime utility function of the form

U = u(ct) + au(cf),

where a is the time discounting parameter, the representative agent (consumer) maximizes his utility when

u'(ct) = a(1+r)u'(cf).

This expression – the Euler equation – implies that the representative agent (consumer) is indifferent between consuming one more unit today or instead consuming it tomorrow. Typically using a logarithmic function form – u(c) = log c – which gives u'(c) = 1/c, the Euler equation can be rewritten as

1/ct = a(1+r)(1/cf),

or

cf/ct = a(1+r).

This importantly implies that according to the neoclassical consumption model changes in the (real) interest rate and consumption move in the same direction. And — it also follows that consumption is invariant to the timing of taxes since wealth — ft + yt + yf/(1+r) — has to be interpreted as present discounted value net of taxes. And so, according to the assumption of Ricardian equivalence, the timing of taxes does not affect consumption, simply because the maximization problem as specified in the model is unchanged. As a result — households cut down on their consumption when governments increase their spendings. Mirabile dictu!

Benchmark DSGE models have paid little attention to the role of fiscal policy, therefore minimising any possible interaction of fiscal policies with monetary policy. This has been partly because of the assumption of Ricardian equivalence. As a result, the distribution of taxes across time become irrelevant and aggregate financial wealth does not matter for the behavior of agents or for the dynamics of the economy because bonds do not represent net real wealth for households.

Incorporating more meaningfully the role of fiscal policies requires abandoning frameworks with the Ricardian equivalence. The question is how to break the Ricardian equivalence? Two possibilities are available. The first is to move to an overlapping generations framework and the second (which has been the most common way of handling the problem) is to rely on an infinite-horizon model with a type of liquidity constrained agents (eg “rule of thumb agents”).

Camillo Tovar

out of the fryingSure, macroeconomic models have to abandon Ricardian equivalence nonsense. But replacing it with “overlapping generations” and “infinite-horizon” models — isn’t that — in terms of realism and relevance — just getting out of the frying pan into the fire? All unemployment is still voluntary. Intertemporal substitution between labour and leisure is still ubiquitous. And the specification of the utility function is still hopelessly off the mark from an empirical point of view.

As one Nobel laureate has it:

Ricardian equivalence is taught in every graduate school in the country. It is also sheer nonsense.

Joseph E. Stiglitz, twitter 

And as one economics blogger has it:

DSGE modeling is taught in every graduate school in the country. It is also sheer nonsense.

Lars Syll, twitter 

  1. January 5, 2018 at 12:17 am

    I think you can be more direct than that. A near-equilibrium model cannot describe a market crash.

    You can easily find many other instabilities in modern economies (the regular rise to dominance by new firms, the runaway aggregation of wealth to fewer and fewer people, …) and conclude economies are always far from equilibrium. DSGE are irrelevant and grossly misleading.

    https://betternature.wordpress.com/my-books/sack-the-economists/

  2. January 5, 2018 at 1:49 am

    The Ricardian Equivalence proposition is a prime example of how the use of representative agents to predict collective outcomes leads us to not edification, but rather to thoroughly stupid conclusions.

    Why is it a fallacy of composition to predict collective results (consumption levels) based on the intertemporal decisions of individual consumers/savers?

    Because markets, being what they are, respond quite differently when 1) an individual agent experiences a gain/loss of disposable income, compared to how they respond when 2) all agents experience the same gain/loss of disposable income.

    If a single individual wins the lottery, shehe will experience a dramatic gain in purchasing power within the marketplace, since hiser ranking within the hierarchy of all disposable incomes will increase dramatically, giving himer a greatly enhanced ability to outbid all others for the scarcest goods/services brought to market.

    But if all individuals “win the same lottery”, then none of them experiences an improvement in their rankings within the hierarchy so none of them improves their ability to outbid each other. I.e., none of them experiences an improvement in their actual purchasing power within the marketplace.

    In less dramatic ways, the same thing occurs whenever “everybody” is given the same income tax cut or if everybody must pay the same increase in taxes. No change in the purchasing power of those taxed occurs if all are experiencing the same reduction in disposable income.

    Knowing this, we cannot rationally assume that the same purchasing power penalty an individual citizen would face if hiser tax obligation alone was increased would be forced on everybody if everybody was required to pay the same penalty. That’s not how markets work.

    This, then, is the ultimate reason why it is irrational to invoke the predicted behavior/decisions of a “representative” agent to try to predict what the impact that a tax increase would have on consumption.

    If all agents have experienced the same reduction in disposable income, then everything that is brought to market will simply be sold at a lower price. In real terms, nothing changes…

  3. Willi Mutschler
    January 5, 2018 at 7:55 am

    You are not describing state of the art DSGE models but are rather characterizing the neoclassical paradigm to which I agree. But there are many models that incorporate both features you find are missing, e.g. FiMod

    http://www.sciencedirect.com/science/article/pii/S026499931100229X

    • Rob Reno
      January 31, 2018 at 9:25 pm

      Willi, can your new and improved DSGE state of the art modeling deal with real-world markets’ Dirty Money and the Naked Truth of the economists utter blindness to dirty monies corrosive impact on society, business, politics, and the real lived in economy of millions of struggling human beings? Because if it can’t it’s little more then mental mathematical masturbation (cuddling with oneself while Rome burns).

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