La fiabilité des prévisions macroéconomiques à court terme : 12 ans d'expériences françaises (1970-1981)

Abstract

This paper considers the accuracy of the short-term economic forecasts of twelve French organizations over the period 1970-1981. Discrepancies between forecast and actual values depend mainly on the macro-economic aggregates and forecasting horizon considered. The absolute error on the rate of growth of real GNP is from 0.8 to 1.3 point while for the annual rate of inflation, it is from 1.1 to 2.1 points. In general, over the period in question, forecasters tend to over-optimism ; real GNP growth being on average overestimated by 0.4 point whereas annual inflation is underestimated by 1.5 point. > From a comparison of the various forecasts with results obtained by so-called « naïve methods », it can be seen that a forecast over a 12 to 18 months horizon normally follows the trend of the recent past. A survey of forecasts by foreign organizations confirms the conclusions of the paper. Nominal variables are underestimated, foreign trade and fluctuations in investment levels are badly forecast while GNP growth is, on the whole, overestimated. From the comparison of forecasting errors between the first and second oil shocks, it seems that, despite turbulence in the world economy, short-term forecasting and trade-cycle analysis have made some progress since, in many cases, the errors have been very considerably reduced.