Identification of equations explaining a continuous variable, e.g., the length of sickness absence spells, by age, cohort and time (ACT), subject to their definitional identity is reconsidered. Various extensions of a linear equation to polynomials are explored. If no interactions between the...

For a panel data regression equation with two-way unobserved heterogeneity, individual-specific and period-specific, ‘within-individual’ and ‘within-period’ estimators, which can be given Ordinary Least Squares (OLS) or Instrumental Variables (IV) interpretations, are considered. A class...

How are substitution in the spatial and in the temporal sense connected? Can estimates based on data with spatial variation be transmitted into values appropriate for exploring temporal variation, and vice versa? This paper, building on, inter alia, Frisch (1959), attempts to give some...

Much of the literature on externalities has considered taxes and direct regulation as alternative policy instruments. Both instruments may in practice be imperfect, reflecting informational deficiencies and other limitations. We analyse the use of taxes and regulation in combination, to control...

We examine the remarkable rise in absenteeism among Norwegian employees since the early 1990's, with particular emphasis on disentangling the roles of cohort, age, and time. Based on a fixed effects model, we show that individual age-adjusted absence propensities have risen even more than...

In this paper some labour market consequences of transitions in the agriculture sector are examined by combining a 20-year unbalanced panel data set from Norwegian farm couples (households) and logit modeling of one-period transition probabilities. The multi-dimensionality of the problem follows...