Apparently, some have been discussing whether the gross increased inequality in the USA is connected with the depressionary conditions we are in. So I thought I would climb on my bicycle and do some arithmetic.
I take it as a stylized fact that an increase in inequality is associated with an increase in the average and marginal propensity to save.
There's something called the Harrod-Domar model of growth. I'm not sure I've ever read Domar. I've certainly read more of Harrod than I have of Domar. So in the sequel, I refer exclusively to Harrod.
Harrod defined three rates of growth: the actual rate, the warranted rate, and the natural rate. Increased inequality can result in the warranted rate exceeding the natural rate. Since the warranted rate is unstable and the actual rate cannot long exceed the natural rate, increased inequality is likely to lead to the actual rate of growth falling below and away from the warranted rate, that is, to depressions.
2.0 Harrod's Model
Harrod's model is fairly simple, but it raises deep questions.
2.1 The Actual Rate
Along a steady state growth path, the ratio, v, of the value of capital to the value of net income is constant:
v = K/Y,where K is the value of the capital stock, and Y is the value of net income. v is known as the capital-output ratio. Thus:
dY/dt = (1/v) dK/dtInvestment, I, is defined to be the change in the value of capital with time. Hence,
(1/Y) dY/dt = (1/v) (I/Y)The left-hand-side of of the above equation is, by definition, the rate of growth, g, of the economy. The equality of investment and savings is an accounting definition in a model with no foreign trade and no government. Therefore,
g = (1/v) (S/Y)Define the savings rate, s:
s = S/YThen, a steady state growth ratio is the ratio of the savings rate to the capital-output ratio:
g = s/vThat is, the (actual) rate of growth is the quotient of the savings rate and the capital-output ratio.
2.2 The Warranted Rate
Suppose the savings rate and the capital-output ratio are as desired by income recipients (consumers) and firms, respectively. This defines Harrod's warranted rate of growth:
gw = sd/vdwhere the subscripts on the right hand side stand for "desired". The warranted rate of growth is being achieved when expectations are being realized and current actions are not setting up forces to disturb current expectations.
The warranted rate of growth extends Keynes' analysis to the long period. Consider the stability of a warranted growth path. If the actual rate of growth exceeds the warranted rate, capacity will be utilized at a greater rate than firms expected. They will increase investment faster than the warranted rate, and the rate of growth will deviate from the warranted rate even more. Likewise, if the actual rate falls below the warranted rate, firms will cut back on investment since the plans upon which their investment was made are not being realized. Hence, the warranted rate is unstable.
Harrod suggested that this instability of the warranted rate is more like an inverted flat-bottomed bowl than a knife-edge.
2.3 The Natural Rate
Suppose the labor force is initially fully employed. Let n be the rate of growth of the labor force:
n = (dL/dt)/LDefine the value of output produced per employed worker:
f = Y/LHarrod-neutral technical change occurs when the value of output per worker grows at a constant rate, m, while the rate of profit stays unchanged:
m = (1/f) df/dtHarrod-neutral technical progress implies that the productivity of labor is growing at the same rate in all industries.
Anyways, the following equation follows:
dY/dt = f dL/dt + L df/dtSome algebra yields:
(1/Y) (dY/dt) = ( 1/L) (dL/dt) + (1/f) (df/dt)The left hand side of the above equation is the rate of growth that keeps the labor force fully employed (or a constant percentage unemployed). Harrod calls this the natural rate of growth. Hence, assuming Harrod-neutral technological progress, the natural rate of growth is the sum of the rate of growth of the labor force and the rate of growth of labor productivity.
gn = n + m
Notice that the determinants of the warranted rate of growth - the savings rate and the desired capital-output ratio - are taken as exogeneous constants. The determinants of the natural rate of growth - the growth of the labor force and Harrod-neutral technological progress - are also given. Hence, the warranted and natural rates can only be equal by a fluke.
Solow, following up on some work by Pivlin, suggested that the desired equality between the warranted and natural rates can be brought about by considering the capital-output ratio as a well-behaved function of the rate of interest. Divergences between the two rates can be corrected by variations in the distribution of income. This approach of neoclassical macroeconomics is exemplified in Solow's eponymous growth model, but it has been shown to be not well-founded in the Cambridge Capital Controversy.
If the warranted rate is below the natural rate, a moderate increase in the saving rate is desirable if the economy is exhibiting boom-like conditions. This would bring the warranted rate towards the actual rate of growth while still keeping it below the natural rate of growth.
Notice that when the warranted rate exceeds the natural rate, the economy must sometime fall below the warranted rate. The natural rate sets a limit which the economy cannot long exceed. Because of the instability of the warranted rate, such an economy will experience frequent and perhaps prolonged recessionary conditions. Since increased savings intensify the discrepancies between the warranted and natural growth rates under these conditions, increased savings intensify the frequency and severity of recessions. That is, increased inequality can intensify the frequency and severity of recessions.
- A. Asimakopulos (1991) Keynes's General Theory and Accumulation, Cambridge.
- Roy F. Harrod (1948) Towards a Dynamic Economics, Macmillan.
- Joan Robinson (1962) Essays in the Theory of Economic Growth, Macmillan.