Investments in education and welfare in a two-sector, random matching economy

We consider a random matching model where heterogeneous agents choose optimally to invest time and real resources in education. Generically, there is a steady state equilibrium, where some agents, but not all of them, invest. Regular steady state equilibria are constrained inefficient in a strong sense. The Hosios (1990) condition is neither necessary, nor sufficient, for constrained efficiency. We also provide restrictions on the fundamentals sufficient to guarantee that equilibria are characterized by overeducation (or undereducation), present some results on their comparative statics properties, and discuss the nature of welfare improving policies.

Income taxes, subsidies to education, and investments in human capital

We study a two-sector economy with investments in human and physical capital and imperfect labor markets. Human and physical capital are heterogeneous. Workers and firms endogenously select the sector they are active in, and choose the amount of their sector-specific investments in human and physical capital. To enter the high-skill sector, workers must pay a fixed cost that we interpret as direct cost of education. Given the distribution of the agents across sectors, at equilibrium, in each sector there is underinvestment in both human and physical capital, due to non-contractibility of investments. A second source of inefficiency is related to the self-selection of the agents into the two sectors. It typically induces too many workers to invest in education. Under suitable restrictions on the parameters, the joint effect of the two distortions is that equilibria are characterized by too many people investing too little effort in the high skill sector. We also analyze the welfare properties of equilibria and study the effects of several tax-subsidy policies on the total expected surplus.

Spectral Shape of Check-Hybrid GLDPC Codes

This paper analyzes the asymptotic exponent of both the weight spectrum and the stopping set size spectrum for a class of generalized low-density parity-check (GLDPC) codes. Specifically, all variable nodes (VNs) are assumed to have the same degree (regular VN set), while the check node (CN) set is assumed to be composed of a mixture of different linear block codes (hybrid CN set). A simple expression for the exponent (which is also referred to as the growth rate or the spectral shape) is developed. This expression is consistent with previous results, including the case where the normalized weight or stopping set size tends to zero. Furthermore, it is shown how certain symmetry properties of the local weight distribution at the CNs induce a symmetry in the overall weight spectral shape function.Comment: 6 pages, 3 figures. Presented at the IEEE ICC 2010, Cape Town, South Africa. A minor typo in equation (9) has been correcte

Growth Rate of the Weight Distribution of Doubly-Generalized LDPC Codes: General Case and Efficient Evaluation

The growth rate of the weight distribution of irregular doubly-generalized LDPC (D-GLDPC) codes is developed and in the process, a new efficient numerical technique for its evaluation is presented. The solution involves simultaneous solution of a 4 x 4 system of polynomial equations. This represents the first efficient numerical technique for exact evaluation of the growth rate, even for LDPC codes. The technique is applied to two example D-GLDPC code ensembles.Comment: 6 pages, 1 figure. Proc. IEEE Globecom 2009, Hawaii, USA, November 30 - December 4, 200

Stability of Iterative Decoding of Multi-Edge Type Doubly-Generalized LDPC Codes Over the BEC

Using the EXIT chart approach, a necessary and sufficient condition is developed for the local stability of iterative decoding of multi-edge type (MET) doubly-generalized low-density parity-check (D-GLDPC) code ensembles. In such code ensembles, the use of arbitrary linear block codes as component codes is combined with the further design of local Tanner graph connectivity through the use of multiple edge types. The stability condition for these code ensembles is shown to be succinctly described in terms of the value of the spectral radius of an appropriately defined polynomial matrix.Comment: 6 pages, 3 figures. Presented at Globecom 2011, Houston, T

Effects of condensed tannins on goats experimentally infected with Haemonchus contortus.

Although the use of tanniferous plants or condensed tannins as an alternative to anthelmintics to control gastrointestinal nematodes has been largely documented in sheep, studies remain scarce in goats. The objective of this study was therefore to assess the possible impact of condensed tannins in goats infected with adult Haemonchus contortus. Two groups of cull goats were experimentally infected with 10.000 L3 of H. contortus. After 4 weeks, quebracho extracts, representing 5% of the diet DM, were administered for 8 days to one of the two groups. Goats of the second group remained as controls. One week after the end of quebracho administration, the goats were euthanised. Individual egg excretion and pathophysiological parameters were measured weekly during the study. At the end of the study, worm counts were assessed and histological samples from the abomasa were taken to count the numbers of mucosal mast cells, globule leukocytes and eosinophils. The administration of tannins was associated with a significant decrease in egg excretion, which persisted until the end of experiment. This reduction was not associated with any difference in worm number but with a significant decrease in female fecundity. No significant changes in the mucosal density of the three inflammatory cell types were detected between the two groups. These results indicate that the major consequence of tannin consumption in goats is a reduction in worm fecundity and egg output, which does not seem related to significant changes in the local mucosal response

Spectral Shape of Doubly-Generalized LDPC Codes: Efficient and Exact Evaluation

This paper analyzes the asymptotic exponent of the weight spectrum for irregular doubly-generalized LDPC (D-GLDPC) codes. In the process, an efficient numerical technique for its evaluation is presented, involving the solution of a 4 x 4 system of polynomial equations. The expression is consistent with previous results, including the case where the normalized weight or stopping set size tends to zero. The spectral shape is shown to admit a particularly simple form in the special case where all variable nodes are repetition codes of the same degree, a case which includes Tanner codes; for this case it is also shown how certain symmetry properties of the local weight distribution at the CNs induce a symmetry in the overall weight spectral shape function. Finally, using these new results, weight and stopping set size spectral shapes are evaluated for some example generalized and doubly-generalized LDPC code ensembles.Comment: 17 pages, 6 figures. To appear in IEEE Transactions on Information Theor

The Dual Face of Empowerment: A Model for Cooperative Resource Building

Homelessness among families with children has become a nationwide problem. Although homelessness is difficult to document, it is estimated that approximately 250,000 to 3,000,000 people in the United States are homeless. Families, which comprise approximately one third of the homeless population, is its fastest growing segment (Mihaly, 1991; National Coalition for the Homeless, 1989; Van Vliet, 1989). This may be a conservative figure. Some of these families often go uncounted because they are part of the invisible homeless. They avoid agency contact for fear of losing their children or live in motels, cars, or campgrounds and thereby are not counted among the homeless (Edelman & Mihaly, 1989)

Interactions between nutrition and gastrointestinal infections with parasitic nematodes in goats

Parasitic nematodes of the digestive tract remain one of the main constraints to goat production both in temperate and tropical countries. The usual mode of control of these gastrointestinal nematodes (GIN) based on the repeated use of anthelmintics is now strongly questioned because of the increasing development of resistance to these molecules. Among the alternative methods to anthelmintics currently available, the manipulation of host nutrition in order to improve the host resistance and/or resilience to parasitic infections seems to represent one of the most promising options to reduce the dependence on conventional chemotherapy and to favour the sustainable control of gastro intestinal nematode infections. This paper will review the available information on the interactions between nutrition and nematode parasitism in dairy or meat goats both in temperate and tropical conditions. It will refer to quantitative aspects of the diet (influence of the protein and/or energy parts) as well as to qualitative components (effects of plant secondary metabolites on worm biology) and will discuss the specificities of goats in regard of theses interactions