Tax Revenue Forecasts in IMF-Supported Programs

Year-ahead forecasts of tax revenues incorporated into IMF programs for low-income countries, from 1993 to 1999, are compared with the corresponding outturns. The accuracy of these forecasts was low, with a mean absolute percentage error of 16 percent. Forecasts of tax revenues as a percentage of GDP were biased upwards, but there was no significant bias in forecasts of nominal tax revenues. Upward bias in the tax revenue forecasts was associated with subsequent interruptions to the program, and the length of time between the commencement of the program and the beginning of the year for which the forecast was made.