A non-regular Groebner fan

The Groebner fan of an ideal $I\subset k[x_1,...,x_n]$, defined by Mora and Robbiano, is a complex of polyhedral cones in $R^n$. The maximal cones of the fan are in bijection with the distinct monomial initial ideals of $I$ as the term order varies. If $I$ is homogeneous the Groebner fan is complete and is the normal fan of the state polytope of $I$. In general the Groebner fan is not complete and therefore not the normal fan of a polytope. We may ask if the restricted Groebner fan, a subdivision of $R_{>=0}^n$, is regular i.e. the normal fan of a polyhedron. The main result of this paper is an example of an ideal in $Q[x_1,...,x_4]$ whose restricted Groebner fan is not regular.Comment: 11 page

On the Wealth Dynamics of Swedish Families 1984-1998

This paper focuses on three issues. First, it analyses the increasing inequality of wealth in Sweden in terms of percentile age and birth cohort differences. Second, it discusses mobility of wealth as a function of age, length of the transition period, the magnitude of quantile differences, and a time trend. The third theme is the relative importance of bequests. Estimates are given of their share of total net worth, and of their contribution to the inequality and mobility of wealth.Wealth distribution; age-cohort effects; wealth mobility; bequests

An Enhanced Perturbational Study on Spectral Properties of the Anderson Model

The infinite-$U$ single impurity Anderson model for rare earth alloys is examined with a new set of self-consistent coupled integral equations, which can be embedded in the large $N$ expansion scheme ($N$ is the local spin degeneracy). The finite temperature impurity density of states (DOS) and the spin-fluctuation spectra are calculated exactly up to the order $O(1/N^2)$. The presented conserving approximation goes well beyond the $1/N$-approximation ({\em NCA}) and maintains local Fermi-liquid properties down to very low temperatures. The position of the low lying Abrikosov-Suhl resonance (ASR) in the impurity DOS is in accordance with Friedel's sum rule. For $N=2$ its shift toward the chemical potential, compared to the {\em NCA}, can be traced back to the influence of the vertex corrections. The width and height of the ASR is governed by the universal low temperature energy scale $T_K$. Temperature and degeneracy $N$-dependence of the static magnetic susceptibility is found in excellent agreement with the Bethe-Ansatz results. Threshold exponents of the local propagators are discussed. Resonant level regime ($N=1$) and intermediate valence regime ($|\epsilon_f| <\Delta$) of the model are thoroughly investigated as a critical test of the quality of the approximation. Some applications to the Anderson lattice model are pointed out.Comment: 19 pages, ReVTeX, no figures. 17 Postscript figures available on the WWW at http://spy.fkp.physik.th-darmstadt.de/~frithjof

On Household Wealth Trends in Sweden over the 1990's

Influenced by major tax reform in the early 1990s and by the exceptional boom in the stock market at the end of that decade, overall wealth in Swedish households increased. So did wealth inequality. The large baby- boom cohorts of the 1940s have been successful in accumulating wealth and they also have large claims on the public pension system. The wealth implicit in the form of these claims dominates private wealth in most Swedish households, and in this paper it is argued that private life- cycle savings have been small in Sweden. Most household saving has been done though the public pension systems. However, concern about the future viability of the pension systems probably increased private life- cycle savings in the 1990s.distribution of wealth, tax reform, pension wealth, age-cohort effects

On Household Wealth Trends in Sweden over the 1990s

Influenced by major tax reform in the early 1990s and by the exceptional boom in the stock market at the end of that decade, overall wealth in Swedish households increased. So did wealth inequality. The large baby- boom cohorts of the 1940s have been successful in accumulating wealth and they also have large claims on the public pension system. The wealth implicit in the form of these claims dominates private wealth in most Swedish households, and in this paper it is argued that private life- cycle savings have been small in Sweden. Most household saving has been done though the public pension systems. However, concern about the future viability of the pension systems probably increased private life- cycle savings in the 1990s.distribution of wealth, tax reform, pension wealth, age-chort effects

Statistical Inference in Micro Simulation Models: Incorporating external information

In practical applications of micro simulation models very little is usually known about the properties of the simulated values. This paper argues that we need to apply the same rigorous standards for inference in micro simulation work as in scientific work generally. If not, then micro simulation models will loose in credibility. The paper first discusses how the structure of the model will determine inference and then follow sections on estimation and validation. Differences between inference in static and dynamic models are noted and then the paper focuses on the estimation of behavioral parameters. There are three themes: calibration viewed as estimation subject to external constraints, piece meal vs. system-wide estimation, and simulation based estimation.Micro simulation; Alignment; Calibration; System-wide estimation; Simulation-based estimation

Towards an Applicable True Cost-of-Living Index that Incorporates Housing

A dynamic model of consumer behavior that incorporates the demand for housing is specified such that it is consistent with the general purpose of a consumer price index. From this model a true cost-of-living index that includes housing is derived. Being an ideal index it cannot be computed without imposing additional assumptions about the behavior of the consumer, but it is possible to draw conclusions about the prices and weights that should be used in conventional approximations to such an ideal index.True cost-of-living index; compensation index; price index of housing

"On Household Wealth Trends in Sweden over the 1990s"

Influenced by major tax reform in the early 1990s and by the exceptional boom in the stock market at the end of that decade, overall wealth in Swedish households increased. So did wealth inequality. The large baby-boom cohorts of the 1940s have been successful in accumulating wealth and they also have large claims on the public pension system. The wealth implicit in the form of these claims dominates private wealth in most Swedish households, and in this paper it is argued that private life-cycle savings have been small in Sweden. Most household saving has been done though the public pension systems. However, concern about the future viability of the pension systems probably increased private life-cycle savings in the 1990s.