(14)For reasons of simplicity and comparability, a downturn period should have a duration of at least 12 months. In order to ensure greater accuracy in the results, that period of time should be treated as a minimum. Institutions should be required to apply a longer duration where the most severe value(s) for the economic indicator(s) associated with a downturn period imply a longer downturn. The duration of a downturn period should reflect adverse conditions in cyclical behaviours specific to the type of exposures under consideration, rather than structural changes in the economy leading to long-term effects on the values of economic indicators.