This paper argues that persistence is not an invariant feature of a time series, but depends on the context in which the series is used: as the parameters of any dynamic model are defined relative to a particular information set, any change in the set of conditioning variables might affect the...

Macroeconomic models usually represent an equilibrium unemployment rate by using a differential equation. The solution of the differential equation expresses the natural unemployment rate. The same result is possible to achieve by using an introduced Markov's model of unemployment. Markov's...