A combinatorical problem is said to be of high computational complexity, if it can be shown that every efficient algorithm needs a high amount of resources as measured in Computing time or storage capacity. This paper will (1) introduce some basic concepts of mathematical complexity theory; (2)...

Aggregation may be harmful but cannot always be avoided in the analysis of complex econometric models. It should be carried out intelligently by choosing ein aggregative model optimally for modes of aggregation speeified in advance, i.e. minimizing the bias introduced by aggregation and...

A widely used method in the analysis of complex econometric models is to replace the "true model" by an aggregative one in which the variables are grouped and replaced by sums or weighted averages of the variables in each group. The analysis of the problem of choosing an aggregative model...

This paper addresses the question why a lot of firms demand stricter environmental regulation. With non-identical producers within the same industry, lobbying for tighter environmental rules turns out to be an important strategy of raising rivals' costs. Furthermore, the paper explains when the...

In diesem Aufsatz wird die nichtparametrische Autoregression auf die Prognose von Quantilen angewendet. Verfahren der Kernregression werden benutzt, um zu autoregressiven Quantiisschätzern zu gelangen. Da die üblichen Maße zur Beurteilung der Prognose, wie etwa der mittlere quadratische...

This paper considers trade policies and welfare in a Harris-Todaro model with risk averse workers. Workers are assumed to have identical and homothetic preferences, but their incomes differ, depending on whether and where they are employed. When workers are equally weighted, maximizing social...

In econometric modelling the choice of relevant variables is of crucial importance for the Interpretation of the results. In many cases it is based on some a priori knowledge from economic theory and a rather heuristic procedure for determining other influential variables sometimes based on an...

The simple Ricardian model explains the comparative cost advantage by a relative productivity advantage of the single factor of production. This model is tested in this paper using microdata of the german business survey. In a first approach labour is being considered to be the only factor of...