There is a long running debate among forecasting professionals, on whether to use Forecast or Actual in the denominator of your percentage error calculations. The Winter 2009 issue of Foresight had an article by Kesten Green and Len Tashman, reporting on a survey (of the International Institute of Forecasters discussion

The Summer 2010 issue of Foresight is now available. Here is Editor Len Tashman’s preview: For so many years, we forecasters have developed and refined models for demand forecasts – forecasts for product and item sales, orders, shipments – without paying adequate attention to the details of how these forecasts

Better forecasting can, of course, help address many business problems. We want to believe that more accurate forecasts are always possible. “If only,” management bemoans, “if only we had bigger computers, more sophisticated software, more skilled forecast analysts – or if the analysts we have just worked harder!” Unfortunately, there