Ownership Structures

In this paper, we analyse the effects of the massive Russian privatisation programme on the ownership of Russian firms and on the behaviour of formerly state owned enterprises. A large random sample of Russian firms is used to investigate the emerging ownership structures, patterns of control and enterprise behaviour. We find that workers have become the dominant owners in a majority ig Russian private firms; 65% of the total as against 19% being manager owned and 16% of being outsider owned. Higher- ownership appears to confer significantly more influence over decision-making on managers and outsiders, but not on workers. Most importantly however, we find no evidence that privatisation affects any major area of enterprise behaviour or performance.

Effects of home-based play-assisted stimulation on developmental performances of children living in extreme poverty : a randomized single-blind controlled trial

Background: Children living with foster families in a resource-limited setting such as Ethiopia are at risk of developmental problems. It is not yet clear whether intensive home-based developmental stimulation assisted by play can reduce these problems. The main objective of this study was to examine the effects of play-assisted intervention integrated into basic services on the developmental performance of children living with foster families in extreme poverty. Methods: A randomized single-blind (investigator) controlled trial design was used. The study was conducted in Jimma, South West Ethiopia. Using computer-generated codes, eligible children of 3-59 months in age were randomly allocated to intervention (n = 39) and control (n = 39) groups at a 1:1 ratio. Children in the intervention group received home-based play-assisted stimulation in addition to the basic services provided to children in both groups. The intervention consisted of an hour of play stimulation conducted during a weekly home visit over the course of six months. Personal-social, language, fine and gross motor outcomes were assessed using Denver II-Jimma, and social-emotional outcome was obtained using an adapted Ages and Stages Questionnaire: Social-Emotional (ASQ: SE). Information about sociodemographic characteristics was collected using a structured questionnaire. Anthropometric methods were used to determine nutritional status. The effects of the intervention on the abovementioned outcomes over the study period and group differences in change over time were examined using Generalized Estimating Equations (GEE). Results: Statistically significant intervention effects were found for language (P = 0.0014), personal-social (P = 0.0087) and social-emotional (P < 0.0001) performances. At the midline of the study, language (effect size = 0.34) and social-emotional (effect size = - 0.603) benefits from the play-assisted stimulation had already been observed for the children in the intervention group. For language, the intervention effect depended on the child's sex (P = 0.0100) and for personal-social performance, on family income (P = 0.0300). Conclusions: Intensive home-based play-assisted stimulation reduced the developmental problems of children in foster families in the context of extreme poverty. Longer follow-up may reveal further improvements in the developmental performance of the children

Intermediate integer programming representations using value disjunctions

We introduce a general technique to create an extended formulation of a mixed-integer program. We classify the integer variables into blocks, each of which generates a finite set of vector values. The extended formulation is constructed by creating a new binary variable for each generated value. Initial experiments show that the extended formulation can have a more compact complete description than the original formulation. We prove that, using this reformulation technique, the facet description decomposes into one ``linking polyhedron'' per block and the ``aggregated polyhedron''. Each of these polyhedra can be analyzed separately. For the case of identical coefficients in a block, we provide a complete description of the linking polyhedron and a polynomial-time separation algorithm. Applied to the knapsack with a fixed number of distinct coefficients, this theorem provides a complete description in an extended space with a polynomial number of variables.Comment: 26 pages, 5 figure

The Discrete Dantzig Selector: Estimating Sparse Linear Models via Mixed Integer Linear Optimization

We propose a novel high-dimensional linear regression estimator: the Discrete Dantzig Selector, which minimizes the number of nonzero regression coefficients subject to a budget on the maximal absolute correlation between the features and residuals. Motivated by the significant advances in integer optimization over the past 10-15 years, we present a Mixed Integer Linear Optimization (MILO) approach to obtain certifiably optimal global solutions to this nonconvex optimization problem. The current state of algorithmics in integer optimization makes our proposal substantially more computationally attractive than the least squares subset selection framework based on integer quadratic optimization, recently proposed in [8] and the continuous nonconvex quadratic optimization framework of [33]. We propose new discrete first-order methods, which when paired with state-of-the-art MILO solvers, lead to good solutions for the Discrete Dantzig Selector problem for a given computational budget. We illustrate that our integrated approach provides globally optimal solutions in significantly shorter computation times, when compared to off-the-shelf MILO solvers. We demonstrate both theoretically and empirically that in a wide range of regimes the statistical properties of the Discrete Dantzig Selector are superior to those of popular $\ell_{1}$-based approaches. We illustrate that our approach can handle problem instances with p = 10,000 features with certifiable optimality making it a highly scalable combinatorial variable selection approach in sparse linear modeling

Macroeconomic adjustment to oil shocks and fiscal reform : simulations for Zimbabwe, 1988-1995

The authors develop and apply a macroeconomic general equilibrium model for Zimbabwe. The model integrates a behavioral estimated model structure, taken from a companion paper, with the relevant budget constraints for a six-sector disaggregation into a comprehensive framework. Starting with 1988 as a base year, the authorssent simulations for a base scenario covering the period 1988-1995. From the different macroeconomic issues and reform requirements identified in the companion paper as relevant for Zimbabwe today, they select two for performing alternative scenario simulations here: a continuation of the current oil shock and strong fiscal stabilization. The oil shock is shown to reduce growth, increase inflation, depreciate the real exchange rate, and reduce private investment in Zimbabwe, a country heavily dependent on imported oil. Fiscal adjustment is a major challenge for stabilization and growth faced by Zimbabwe's policy-makers today. The paper's simulations show that deep fiscal reform will significantly help Zimbabwe achieve a sustainable debt path, a decline in interest rates paid on public debt, and a recovery of private consumption and investment.Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Economic Stabilization,International Terrorism&Counterterrorism