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6.7 Real Business Cycle Theory

The modern new classical research programme starts from the position that

‘growth and fluctuations are not distinct phenomena to be studied with separate

data and different analytical tools’ (Cooley, 1995). The REBCT research programme

was initiated by Kydland and Prescott (1982), who in effect took up

the challenge posed by Lucas (1980a) to build an artificial imitation economy

capable of imitating the main features of actual economies. The artificial

economy consists of optimizing agents acting in a frictionless perfectly competitive

environment that is subject to repeated shocks to productivity. Although

the second phase of new classical macroeconomics has switched emphasis

away from monetary explanations of the business cycle, the more recently

developed equilibrium models have retained and refined the other new classical

building blocks.

Following Frisch (1933) and Lucas (1975, 1977), real business cycle theorists

distinguish between impulse and propagation mechanisms. An impulse

mechanism is the initial shock which causes a variable to deviate from its

steady state value. A propagation mechanism consists of those forces which

carry the effects of the shock forward through time and cause the deviation

from the steady state to persist. The more recent brand of new classical

equilibrium theories have the following general features (Stadler, 1994):

1. REBCT utilizes a representative agent framework where the agent/household/

firm aims to maximize their utility or profits, subject to prevailing

resource constraints.

2. Agents form expectations rationally and do not suffer informational

asymmetries. While expected prices are equal to actual prices, agents

may still face a signal extraction problem in deciding whether or not a

particular productivity shock is temporary or permanent.

3. Price flexibility ensures continuous market clearing so that equilibrium

always prevails. There are no frictions or transaction costs.

4. Fluctuations in aggregate output and employment are driven by large

random changes in the available production technology. Exogenous shocks

to technology act as the impulse mechanism in these models.

5. A variety of propagation mechanisms carry forward the impact of the

initial impulse. These include the effect of consumption smoothing, lags

in the investment process (‘time to build’), and intertemporal labour


6. Fluctuations in employment reflect voluntary changes in the number of

hours people choose to work. Work and leisure are assumed to be highly

substitutable over time.

7. Monetary policy is irrelevant, having no influence on real variables, that

is, money is neutral.

8. The distinction between the short run and the long run in the analysis of

economic fluctuations and trends is abandoned.

It can be seen from the above that the major changes from MEBCT are with

respect to: (i) the dominant impulse factor, with technological shocks replacing

monetary shocks; (ii) the abandonment of the emphasis given to imperfect

information as regards the general price level which played such a crucial

role in the earlier monetary misperception models inspired by Lucas; and (iii)

the breaking down of the short-run/long-run dichotomy in macroeconomic

analysis by integrating the theory of growth with the theory of fluctuations.

The lack of clear supporting evidence from econometric work on the causal

role of money in economic fluctuations was generally interpreted as providing

a strong case for shifting the direction of research towards models where

real forces play a crucial role. As we have already seen, this case was further

strengthened by the findings of Nelson and Plosser (1982) that most macroeconomic

time series are better described as a random walk, rather than as

fluctuations or deviations from deterministic trends. Real business cycle theorists

also claim that their theories provide a better explanation of the ‘stylized

facts’ which characterize aggregate fluctuations. Indeed, they have challenged

much of the conventional wisdom with respect to what are the stylized facts

(see section 6.14 below).