Forecasting accuracy and the assumption of constancy

Statistical forecasting is based on the assumption of constancy, or structural ability in the data. This paper argues that such an assumption might not always be realistic in real life forecasting situations. Unfortunately, however, statisticians and forecasters tend to forget, or at least not make explicit this important assumption, thus creating false expectations which cannot be realistically fulfilled. The paper proposes a wider role for forecasting and makes specific suggestions to overcome the problems arising when the assumption of constancy does not hold.