On measures of instability and indentification of trends: A revised procedure

Recent theoretical and practical interest has been directed towards the investigation of short-term instability in economic variables, also in view of its impact on long-term growth. For instance, domestic investment and import capacity can be hampered by both a structural deterioration in the terms of trade, and high fluctuations in export earnings. Nevertheless, instability is generally studied by applying deterministic trend models on relatively short time series. This study aims at redressing some drawbacks of a common procedure, which, particularly for series with one or more breaks, is not fully appropriate in terms of selection of trends and measurement of instability. An amended version of this procedure is applied to 1960–85 mineral price series.