But this does not imply that there is some magical threshold defining “acceptable” and “unacceptable” rates of earnings growth. In the short run, the link between earnings growth and inflation is complicated by a whole host of factors, including exchange rate movements, cyclical variations in productivity and profit margins, irregular bonus payments, and one-off adjustments to tax rates and other “wedge” effects. It is true that given the UK’s historical levels of annual productivity growth of around 2% and the inflation target of 22%, it would be a cause for concern to the MPC if average earnings increased by much more – or much less – than 4.5% a year over a prolonged period without there being a corresponding change in trend productivity growth. That is not because the Committee has a view about the appropriate level of pay awards. It is not our job to second-guess what businesses should or should not pay their employees. Nor is it because we think earnings growth causes inflation – inflation is a monetary phenomenon. Rather it is because sustained earnings growth much above or below these rates may indicate that the level of utilisation in the labour market has reached a level inconsistent with the inflation target. The June meeting of the MPC drew particular attention to the rise in headline earnings growth as measured by the Average Earnings Index. But that should be viewed against a background of increasing concern about the tightness of the labour market.
Second, the temporary improvement in the terms of trade that followed the rise in sterling in 1996 reduced the wedge between the real consumption wage – which is of relevance to employees and which reflects a mix of both domestic and imported inflation components – and the real product wage – which is of relevance to employers and which reflects the prices only of domestically produced goods. That reduction in the wedge is likely to have reduced the pressure on nominal wage growth for any given level of unemployment. So it is quite possible to believe that the NAIRU has fallen even if the natural rate has not. But this is likely to be temporary. As the impact of sterling’s appreciation on wages and prices wears off, the NAIRU will, other things being equal, rise towards the natural rate. But other more BIS Review 103/1998  –5–  lasting changes may reduce the natural rate (and hence the NAIRU). For example, a range of government policies, including changes to the Jobseekers Allowance, the New Deal and the new Working Families Tax Credit, have increased incentives to work. The National Minimum Wage works in the opposite direction. Assessing the impact of these structural factors on the natural rate is no easier than calculating the effect of macroeconomic shocks on the NAIRU. But it is useful to distinguish the two concepts, not least because they can move quite differently in the short run. Enough of this theory, some of which may appear largely semantic.