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6.9 Technology shocks

Although some versions of real business cycle theory allow for real demand

shocks, such as changes in preferences or government expenditures, to act as

the impulse mechanism, these models are more typically driven by exogenous

productivity shocks. These stochastic fluctuations in factor productivity

are the result of large random variations in the rate of technological change.

The conventional Solow neoclassical growth model postulates that the growth

of output per worker over prolonged periods depends on technological progress

which is assumed to take place smoothly over time. Real business cycle

theorists reject this view and emphasize the erratic nature of technological

change which they regard as the major cause of changes in aggregate output.

To see how aggregate output and employment vary in a real business cycle

model, consider Figure 6.3. Panel (a) of Figure 6.3 illustrates the impact of a

beneficial technology shock, which shifts the production function from Y to

Y*. The impact of this shift on the marginal product of labour and hence the

demand for labour is shown in panel (b). By increasing the demand for labour

a productivity shock raises employment as well as output. How much employment

expands will depend on the elasticity of labour supply with respect

to the current real wage. The ‘stylized facts’ of the business cycle indicate

that small procyclical variations in the real wage are associated with large

procyclical variations of employment. Thus a crucial requirement for real

business cycle theory to be consistent with these facts is for the labour supply

schedule to be highly elastic with respect to the real wage, as indicated in

panel (b) by SL2. In this case a technology shock will cause output to expand

from Y0 to Y2 with the real wage increasing from (W/P)a to (W/P)c, and

employment increasing from L0 to L2. If the labour supply schedule is relatively

inelastic, as shown by SL1, large variations of the real wage and small

changes in employment would result from a technology shock. However, this

does not fit the stylized facts.

It is clear that, in order for real business cycle theories to explain the

substantial variations in employment observed during aggregate fluctuations,

there must be significant intertemporal substitution of leisure. Since in these

models it is assumed that prices and wages are completely flexible, the labour

market is always in equilibrium. In such a framework workers choose unemployment

or employment in accordance with their preferences and the

opportunities that are available. To many economists, especially to those with

a Keynesian orientation, this explanation of labour market phenomena remains

unconvincing (Mankiw, 1989; Tobin, 1996).

Figure 6.3 Output and employment fluctuations due to a technology shock