On Measuring Non-Recursive Trade-Offs

We investigate the phenomenon of non-recursive trade-offs between descriptional systems in an abstract fashion. We aim at categorizing non-recursive trade-offs by bounds on their growth rate, and show how to deduce such bounds in general. We also identify criteria which, in the spirit of abstract language theory, allow us to deduce non-recursive tradeoffs from effective closure properties of language families on the one hand, and differences in the decidability status of basic decision problems on the other. We develop a qualitative classification of non-recursive trade-offs in order to obtain a better understanding of this very fundamental behaviour of descriptional systems

An empirical analysis of factors affecting the productivity of livestock in southern Botswana

This study attempts to identify factors responsible for differences in the productivity of cattle managed by private and communal livestock farmers in the southern region of Botswana during 1999/2000. Sample survey data are used to estimate the parameters of a block recursive regression model. Some of the equations postulated in the model are estimated with two-stage least squares (2SLS) to account for likely correlation between endogenous explanatory variables and the error term. The results show that (a) respondents with secure land tenure (private farms) and larger herds use more agricultural credit than do those who rely on open access communal grazing to raise cattle; (b) secure tenure and higher levels of liquidity from long-term credit and off-farm wage remittances promote investment in fixed improvements to land; (c) liquidity from short-term credit and wage remittances supports expenditure on operating inputs; and (d) herd productivity increases with greater investment in operating inputs and fixed improvements, and is therefore positively (but indirectly) influenced by secure land tenure. It can be inferred that government should (a) uphold private property rights to land where they already exist; (b) privatise open access grazing to individual owner-operators where this is politically, socially and economically feasible; and (c) where privatisation to individuals is not feasible, government should encourage users to convert the grazing into common property by subsidising the transaction costs of defining user groups and the boundaries of their resources, and of negotiating and enforcing rules limiting individual use of common property. This first-step in a gradual shift towards private property might be followed by a conversion of user-groups into non-user groups organised along the lines of investor-owned firms where members exchange use rights for benefits rights.Productivity Analysis,

Livestock Market Integration and Price Discovery: Case of Mali

Replaced with revised version of paper 02/22/11.cointegration, structural breaks, market integration, Agricultural and Food Policy, Demand and Price Analysis, International Development, Livestock Production/Industries,

Gender and Competition between Child Economic or Non-Economic Labor and Schooling: Evidence from EPAM Mali

This paper uses the Understanding Children?s Work (UCW) definition of child labor and data from EPAM Mali to highlight the gender difference in the competition between children?s economic or non-economic labor and schooling. A Quadri-variate Probit estimation was first used to account for the interdependency between school and various kinds of child labor: household chores (HHC), market-oriented (MO) activities and non-market-oriented (NMO) activities. Then, a Clogit estimation was used to examine the incidence of time repartition among children within the household regarding the probability of schooling. Empirical results from EPAM Mali provide interesting findings, including differential gender socialization according to the gender of the offspring, gender bias in repartition of tasks and time, and competition between labor activities and schooling.Gender; Education; Child-labor; Intra-household allocations

Anorexia, Body Image and Peer Effects: Evidence from a Sample of European Women

Excessive preoccupation with self-image (or identity) is regarded as a factor contributing to the proliferation of food disorders, especially among young women. This paper models how self-image and peer effects influence health-related behaviours, specifically food disorders. We empirically test our claims using data from the European survey. Our findings suggest that the larger the peers' body-mass, the lower the likelihood of being anorexic. Self-image is correlated with body weight. We use several definitions of peers' body mass and we find that all are negatively associated with the likelihood of women being thin or extremely thin.self-image, identity, body image, eating disorders, anorexia, European women

Fatter Attraction: Marital Status and the Relationship between BMI and Labor Supply

We empirically analyze the labor supply choices of married men and women according to their body size (BMI), using data from the Panel Study of Income Dynamics on anthropometric characteristics of both spouses, and unmarried men and women as comparison group. Heavier husbands are found to work significantly more hours and earn more labor income, controlling for both spouses’ demographic and socioeconomic characteristics. Conversely, no such effect is found for either unmarried individuals or for married women. We suggest a marriage market mechanism through which male BMI and earnings are positively related. Heavier married men compensate for their negative physical trait by providing their wives with more disposable income, working more hours and earning more. Heavier women may not able to compensate their spouse through labor supply, as female physical traits are more relevant in the marriage market than the corresponding male traits.Body Size, Labor Supply, Earnings, Marriage

Child labour and school attendance: Evidence from selection on observed and unobserved variables in Zambia

Although the determinants of child labour and school attendance are well established in the literature, the causal effect of child labour on school attendance is largely unexplored owing in part to econometric challenges. The difficult in finding a valid and strong instrument for child labour, which is argued to be interdependent with school attendance, is one such impediment. Recognizing this difficult and the fact that children in child labour differ from their counterparts who are not in child labour along an array of observed and unobserved characteristics, I proceed along an alternative path in this paper. I examine the causal effect of long run child labour on children current school attendance using a novel estimation method that assumes that the amount of selection on observed variables closely approximates the amount of selection on unobservables. Using data for children between 5 and 17 years in Zambia, empirical results show that child labour has a significant negative effect on the probability of school attendance. The point estimate is also robust to unobserved variables. Results also show that children who participate in child labour are relatively older, hardly live with their mothers, mostly live in rural areas and are found in households were parents or household heads are relatively older and spent less time in school

Learning Interpretable Rules for Multi-label Classification

Multi-label classification (MLC) is a supervised learning problem in which, contrary to standard multiclass classification, an instance can be associated with several class labels simultaneously. In this chapter, we advocate a rule-based approach to multi-label classification. Rule learning algorithms are often employed when one is not only interested in accurate predictions, but also requires an interpretable theory that can be understood, analyzed, and qualitatively evaluated by domain experts. Ideally, by revealing patterns and regularities contained in the data, a rule-based theory yields new insights in the application domain. Recently, several authors have started to investigate how rule-based models can be used for modeling multi-label data. Discussing this task in detail, we highlight some of the problems that make rule learning considerably more challenging for MLC than for conventional classification. While mainly focusing on our own previous work, we also provide a short overview of related work in this area.Comment: Preprint version. To appear in: Explainable and Interpretable Models in Computer Vision and Machine Learning. The Springer Series on Challenges in Machine Learning. Springer (2018). See http://www.ke.tu-darmstadt.de/bibtex/publications/show/3077 for further informatio

Algorithms and lower bounds in finite automata size complexity

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 97-99).In this thesis we investigate the relative succinctness of several types of finite automata, focusing mainly on the following four basic models: one-way deterministic (1)FAs), one-way nondeterministic (1NFAs), two-way deterministic (2DFAS), and two-way nondeterministic (2NFAS). First, we establish the exact values of the trade-offs for all conversions from two-way to one-way automata. Specifically, we prove that the functions ... return the exact values of the trade-offs from 2DFAS to 1DFAS, from 2NFAS to 1DFAs, and from 2DFAs or 2NFAS to 1NFAs, respectively. Second, we examine the question whether the trade-offs from NFAs or 2NFAS to 2DiFAs are polynomial or not. We prove two theorems for liveness, the complete problem for the conversion from 1NFAS to 2DFAS. We first focus on moles, a restricted class of 2NFAs that includes the polynomially large 1NFAS which solve liveness. We prove that, in contrast, 2DFA moles cannot solve liveness, irrespective of size.(cont.) We then focus on sweeping 2NFAS, which can change the direction of their input head only on the end-markers. We prove that all sweeping 2NFAs solving the complement of liveness are of exponential size. A simple modification of this argument also proves that the trade-off from 2DFAS to sweeping 2NFAS is exponential. Finally, we examine conversions between two-way automata with more than one head-like devices (e.g., heads, linearly bounded counters, pebbles). We prove that, if the automata of some type A have enough resources to (i) solve problems that no automaton of some other type B can solve, and (ii) simulate any unary 2DFA that has additional access to a linearly-bounded counter, then the trade-off from automata of type A to automata of type B admits no recursive upper bound.by Christos Kapoutsis.Ph.D

Out of Sight, Out of Mind: Migration, Entrepreneurship and Social Capital

The aim of this paper is to investigate whether return migrants are more likely to become entrepreneurs than non-migrants. We develop a theoretical search model that puts forward the trade off faced by returnees since overseas migration provides an opportunity for human and physical capital accumulation but, at the same time, may lead to a loss of social capital back home. We test the predictions of the model using data from Egypt. We find that, even after controlling for the endogeneity of the temporary migration decision, an overseas returnee is more likely to become an entrepreneur than a non-migrant. Although migrants lose their original social networks whilst overseas, savings and human capital accumulation acquired abroad over-compensate for this loss. Our results also suggest that social networks have no significant impact on becoming entrepreneurs for returnees but matter for non-migrants.social capital, entrepreneurship, selection, savings