Inexactness of the Hydro-Thermal Coordination Semidefinite Relaxation

Hydro-thermal coordination is the problem of determining the optimal economic dispatch of hydro and thermal power plants over time. The physics of hydroelectricity generation is commonly simplified in the literature to account for its fundamentally nonlinear nature. Advances in convex relaxation theory have allowed the advent of Shor's semidefinite programming (SDP) relaxations of quadratic models of the problem. This paper shows how a recently published SDP relaxation is only exact if a very strict condition regarding turbine efficiency is observed, failing otherwise. It further proposes the use of a set of convex envelopes as a strategy to successfully obtain a stricter lower bound of the optimal solution. This strategy is combined with a standard iterative convex-concave procedure to recover a stationary point of the original non-convex problem.Comment: Submitted to IEEE PES General Meeting 201

Foreign Ownership, Employment and Wages in Brazil: Evidence from Acquisitions, Divestments and Job Movers

How much do developing countries benefit from foreign investment? We contribute to this question by comparing the employment and wage practices of foreign and domestic firms in Brazil, using detailed matched firm-worker panel data. In order to control for unobserved worker differences, we examine both foreign acquisitions and divestments and worker mobility, including the joint estimation of firm and worker fixed effects. We find that changes in ownership do not tend to affect wages significantly, a result that holds both at the worker- and firm-levels. However, divestments are related to large job cuts, unlike acquisitions. On the other hand, movers from foreign to domestic firms take larger wage cuts than movers from domestic to foreign firms. Moreover, on average, the fixed effects of foreign firms are considerably larger than those of domestic firms, while worker selection effects are relatively small.foreign direct investment; ownership changes; worker mobility

A logic for n-dimensional hierarchical refinement

Hierarchical transition systems provide a popular mathematical structure to represent state-based software applications in which different layers of abstraction are represented by inter-related state machines. The decomposition of high level states into inner sub-states, and of their transitions into inner sub-transitions is common refinement procedure adopted in a number of specification formalisms. This paper introduces a hybrid modal logic for k-layered transition systems, its first-order standard translation, a notion of bisimulation, and a modal invariance result. Layered and hierarchical notions of refinement are also discussed in this setting.Comment: In Proceedings Refine'15, arXiv:1606.0134

Is firm performance driven by fairness or tournaments? Evidence from Brazilian matched data

Theory and evidence are ambiguous about the effect of within-firm wage inequality on firm performance. This paper tests empirically this relationship drawing on detailed Brazilian matched employer-employee panel data, considering alternative measures of inequality and performance and different estimation methods. We find overwhelming evidence of a positive relationship between wage dispersion and firm performance when using cross-section analysis, especially in manufacturing. However, this relationship is weakened when controlling for firm time-invariant heterogeneity.Tournaments, Incentives, Equity, Wage Dispersion

Foreign Ownership, Employment and Wages in Brazil: Evidence from Acquisitions, Divestments and Job Movers

How much do developing countries benefit from foreign investment? We contribute to this question by comparing the employment and wage practices of foreign and domestic firms in Brazil, using detailed matched firm-worker panel data. In order to control for unobserved worker differences, we examine both foreign acquisitions and divestments and worker mobility, including the joint estimation of firm and worker fixed effects. We find that changes in ownership do not tend to affect wages significantly, a result that holds both at the worker- and firm-levels. However, divestments are related to large job cuts, unlike acquisitions. On the other hand, movers from foreign to domestic firms take larger wage cuts than movers from domestic to foreign firms. Moreover, on average, the fixed effects of foreign firms are considerably larger than those of domestic firms, while worker selection effects are relatively small.ownership changes, foreign direct investment, worker mobility

Foreign Ownership, Employment and Wages in Brazil: Evidence from Acquisitions, Divestments and Job Movers

How much do developing countries benefit from foreign investment? We contribute to this question by comparing the employment and wage practices of foreign and domestic firms in Brazil, using detailed matched firm-worker panel data. In order to control for unobserved worker differences, we examine both foreign acquisitions and divestments and worker mobility, including the joint estimation of firm and worker fixed effects. We find that changes in ownership do not tend to affect wages significantly, a result that holds both at the worker- and firm-levels. However, divestments are related to large job cuts, unlike acquisitions. On the other hand, movers from foreign to domestic firms take larger wage cuts than movers from domestic to foreign firms. Moreover, on average, the fixed effects of foreign firms are considerably larger than those of domestic firms, while worker selection effects are relatively small.Foreign Direct Investment, Ownership Changes, Worker Mobility

Is There Rent Sharing in Developing Countries? Matched-Panel Evidence from Brazil

We provide evidence about the determinants of the wage structures of developing countries by examining the case of Brazil. Our specific question is whether Brazil's dramatic income and wage differentials can be explained by the division of rents between firms and their employees, unlike in competitive labour markets. Using detailed individual-level matched panel data, covering a large share of manufacturing firms and more than 30 million workers between 1997 and 2002, we consider the endogeneity of profits, by adopting different measures of rents and different instruments and by controlling for spell fxed effects. Our results, robust to different specifications and tests, indicate no evidence of rent sharing. This conclusion contrasts with findings for most developed countries, even those with flexible labour markets. Possible explanations for the lack of rent sharing include the weakness of labour-market institutions, the high levels of worker turnover and the macroeconomic instability faced by the country.Wage Bargaining, Instrumental Variables, Matched Employer-Employee Data, Developing Countries