There are three shortcomings of the Hayekian triangle I wish to bring to light.
1) Empirically, prices in all stages of production tend to move together.
2) Related to critique 1, the Hayekian triangle assumes an economy at full employment equilibrium.
3) The Hayekian triangle is an incoherent representation of the macroeconomy.
In his book, Risk and Business Cycles, Tyler Cowen considers points 1) and 2)
Positive comovement [in prices of goods at both the early and latter stages of production] poses a dilemma for theories of the business cycle which start with the assumption of full employment. Comovement requires that all, or nearly all sectors of the economy expand at once, as we usually find in the data. (30)
This poses a problem for Hayek’s analysis where resources are moving from the latter stages to the earlier stages of production. This process is depicted below (Prices and Production, 44, 52).
Notice that the triangle gained two rows. This gain comes at the loss of the length of the already existent rows. That is, investment increases at the expense of consumption in the early stages of the boom. Hayek’s model is a static one where the economy starts at a full-employment equilibrium. In the case of credit expansion it is pushed from this equlibrium. Consumption does not reduce to compensate for the lengthening of production and there is even an increase in consumption as wages rise. Consumers compete with producers for resources in an unsustainable boom that is inevitably followed by a bust. Hayek’s model describes an aspect of reality, but how significant is that aspect? Is artificial expansion of credit necessary for this scenario?
The model assumes that the economy is at the edge of the PPF, that it is at a full-employment equilibrium. A more likely scenario is that the economy is constantly oscillating between the edge of the PPF and the origin. Of course, an economy with well-functioning markets likely operates in greater proximity to the PPF than the origin. Central bank intervention will distort this natural fluctuation, though it is unclear in what ways and to what extent. The state of the economy is always in flux, so the same intervention will not always lead to the same results. The assumption of full employment equilibrium obscures the interaction between natural fluctuations and central bank intervention, and thus the model overemphasizes a unique case. This might be corrected by expanding the model to include different levels of employment.
As a model of the macroeconomy the triangle is represents a snapshot at a given point in time. In this interpretation, the triangle is an aggregation which describes the macro economy in a misleading manner. We might represent an individual good in Hayekian form, and trace out changes in different stages with only minor distortion, but when used to represent the entire economy the triangle must implicitly assume price levels similar to those for which he critiques his peers. In his critique of Hawtrey’s discussion of the price level Hayek writes,
But the main concern of this type of theory is avowed, with certain suppositions ‘tendencies, which affect all prices equally, or at any rate, impartially, at the same time in the same direction.’ And it is only after the alleged causal relation between changes in the quantity of money and average prices has thus been established that effects on relative prices are considered. (5)
But Hayek refers to the price ratios between the stages of production. In referring to the macro economy, he must be referring to the ratio of price levels between the stages (assuming that stages can be neatly represented at this level of analysis). Hayek did not to apply this critique to his own theory.
As a representation of the macro economy, the triangle also errs in predicting the nature of new investments. Consider Hawtrey’s critique of Hayek’s stages.
It is quite likely that the additional investment will be predominantly in the earlier stages, but it is not necessarily so. It might happen that the next most remunerative openings for investment are mainly or exclusively among the later stages. There is no necessary connection between the margin of investment and the stages, and the introduction of the stages into the exposition of the extension of investment serves no useful purpose. (243)
There may be a tendency for increased investment in the
later earlier stages, but that tendency ought not
preclude a broadening of the triangle’s base. Hawtrey also argues that there is
a continual deepening of the capital structure during booms and depressions.
Expansion may augment this deepening but it can also broaden the capital
structure during the boom period if there are unrealized gains in the later
stages that result from the lowering of the interest rate.
Unlike the problem first discussed, I am not sure that these last two can be easily corrected. In terms of macroeconomic analysis, we are left with a triangle whose usefulness is exceeded by its obscurantism.