Although it is not possible, in general, to give a macro description of a micro model over the entire state space of the micro model, it is possible to aggregate exactly over a subspace. The set of micro states where aggregation is possible forms the aggregation set. The paper considers the...

The seasonal adjustment method proposed by Schlicht (1981) can be viewed as a method that minimizes non-stochastic deviations (perturbations). This interpretation gives rise to a critique of the seasonality criterion used there. A new seasonality criterion is proposed that avoids these...

The paper discusses a new seasonality hypothesis which is one part of a weighted regression approach for the decomposition of a time series into a trend, a seasonal component and an irregular component. It is shown that there exists a regression formulation leading, as in the descriptive...

(Approximation by Moving Equilibrium). The analysis of multivariate dynamical models can sometimes be considerably simplified by the assumption that one or several variables move infinitely fast to their equilibrium values. The method is known as the 'moving equilibrium method'. Various...

The analysis of multivariate dynamical models can sometimes be considerably simplified by the assumption that one or several variables move infinitely fast to their equilibrium values. The method is known as the ‘moving equilibrium method’. Various dynamical theories that build on...