Existence of a competitive equilibrium in a one sector growth model with heterogeneous agents and irreversible investment

Summary. We prove existence of a competitive equilibrium in a version of a Ramsey (one sector) model in which agents are heterogeneous and gross investment is constrained to be non negative. We do so by converting the infinite-dimensional fixed point problem stated in terms of prices and commodities into a finite-dimensional Negishi problem involving individual weights in a social value function. This method allows us to obtain detailed results concerning the properties of competitive equilibria. Because of the simplicity of the techniques utilized our approach is amenable to be adapted by practitioners in analogous problems often studied in macroeconomics. Received: September 13, 2001; revised version: December 9, 2002 RID="*" ID="*" We are grateful to Tapan Mitra for pointing out errors as well as making very valuable suggestions. Thanks are due to Raouf Boucekkine and Jorge Duran for additional helpful discussions. We also thank an anonymous referee for his/her helpful comments. The second author acknowledges the financial support of the Belgian Ministry of Scientific Research (Grant ARC 99/04-235 “Growth and incentive design”) and of the Belgian Federal Goverment (Grant PAI P5/10, “Equilibrium theory and optimization for public policy and industry regulation”). Correspondence to: C. Le Van     

Investment in quality upgrade and regulation of the internet

This paper studies the investment decision by a monopolistic internet service provider (ISP) in different regulatory environments. We consider that the ISP can technically provide separate quality upgrades to two vertically differentiated content providers (CPs). Our results show that if unregulated, the ISP could optimally provide asymmetric quality upgrades to both CPs, in favor of the high-quality CP. This subsequently increases the degree of content differentiation, softening competition between the CPs. Imposing a nondiscrimination regulation that forces the ISP to provide an equal quality upgrade to both CPs, however, reduce the ISP’s investment incentive and social welfare. Furthermore, the social planner provides preferential treatment to the high-quality CP if the degree of substitutability is sufficiently low. In contrast, it is socially optimal to prioritize the low-quality CP if the contents are sufficient substitutes, or provide exclusivity if vertical differentiation is high.

     

Diversification evidence from international equity markets using extreme values and stochastic copulas

Tail dependence plays an important role in financial risk management and determination of whether two markets crash or boom together. However, the linear correlation is unable to capture the dependence structure among financial data. Moreover, given the reality of fat-tail or skewed distribution of financial data, normality assumption for risk measure may be misleading in portfolio development. This paper proposes the use of conditional extreme value theory and time-varying copula to capture the tail dependence between the Australian financial market and other selected international stock markets. Conditional extreme value theory enables the model adequacy and the tail behavior of individual financial variable, while the time-varying copula can fully disclose the changes of dependence structure over time. The combination of both proved to be useful in determining the tail dependence. The empirical results show an outperformance of the model in the analysis of tail dependence, which has an important implication in cross-market diversification and asset pricing allocation.     

The impact of minimum wages on employment of low‐wage workers

This study provides empirical evidence on the impact of a minimum wage increase on employment of workers in the formal sector who have wages below the minimum level in Vietnam. Using the difference‐in‐differences with propensity score matching and the Vietnam Household Living Standard Surveys of 2004 and 2006, the article finds that the minimum wage increase in 2005 reduced the proportion of workers having a formal sector job among low‐wage workers. Most workers who lost formal sector jobs became self‐employed.     

Informal Credit,Usury, or Support? A Case Study for Vietnam

The informal credit market remains an important source of finance for the poor in Vietnam. Yet, little if anything is known about the impact of informal loans on poverty and inequality, and the Vietnamese government has no policies towards the informal credit market. In the present study paper, we found that the effect of credit from friends and relatives on per capita expenditure is positive but not statistically significant. Meanwhile, the effect of credit from private moneylenders on per capita expenditure is positive and statistically significant. Borrowing from private moneylenders increases per capita expenditure of households by around 15%. Further, it reduced the poverty incidence of borrowers by around 8.5 percentage points in 2006 and significantly decreases the poverty gap index and the poverty‐severity index. Borrowing from private moneylenders also reduces expenditure inequality, albeit at a very small magnitude.     

A never-decisive and anonymous criterion for optimal growth models

We address in this paper the question of the existence of a Social Welfare Function that would be sustainable and would allow us to obtain solutions to optimal growth models. We define sustainability by two new axioms called Never-decisiveness of the present and Never-decisiveness of the future. We first show that a SWF which has Never-decisiveness properties cannot be defined on a ball of $l_{\infty }^{+}$ . We must (i) restrict to the set of utility streams for which the value of the SWF is finite and (ii) introduce additional assumptions in order to obtain the Never-decisiveness properties. Our main result in this paper is therefore to show that the undiscounted utilitarian criterion is an anonymous and never-decisive criterion for optimal growth models. We consider the set of utilities of consumptions which are generated by a specific technology, namely a technology with decreasing returns for high levels of capital, and restrict ourselves to good programs, i.e., any program for which intertemporal utility is well defined.     

Equal opportunity and poverty reduction: How should aid be allocated?

This paper analyzes a model of aid allocation equalizing the opportunity between recipient countries to reach a common poverty reduction goal. We propose a fair and efficient aid allocation based on a multicriteria principle. The model considers structural handicaps in recipient countries in terms of lack of human capital and economic vulnerability, their initial poverty, and the natural gap between the growth rate required to reach a development goal and the observed one. We show that our proposed aid allocation favors poor and vulnerable countries with our multicriteria principle. It substantially differs from the observed allocation. Analyses also shed light on the impact of the donors' aversion to the low natural growth gap in recipient countries on the optimal aid allocation and the marginal efficiency of aid.     

Competition with asymmetric regulation of mobile termination charges

The aim of this paper is to explore the effectiveness of asymmetric regulation, which allows a new mobile network operator to set higher termination rates than the incumbent operator. We assume that there are two market segments: one in which operators compete on equal terms, with a new technology, and the other in which the entrant is at a disadvantage since the technology it offers is inferior to the incumbent??s. Results show that asymmetric regulation can create favorable conditions that allow the entrant to strengthen its market positioning, and enhance consumer net utilities and social welfare. This highlights the importance of the degree of network asymmetry and the ways in which consumers are split between the two market segments. Lastly, we show that asymmetric regulation can create greater investment incentives for the entrant which could effectively enhance social welfare. These findings can provide useful insights for regulatory policy.     

Research collaboration model in academic social networks

ABSTRACT

This paper proposes a hybrid collaboration recommendation method that accounts for research similarities and the previous research cooperation network. Research cooperation is measured by combining the collaboration time and the number of co-authors who already collaborated with at least one scientist. Research similarity is based on authors’ previous publications and academic events they attended. A weighted directed graph is built to discover new collaborators by using direct and indirect connections between scientists. Moreover, a consensus-based system is built to integrate bibliography data from different sources. The experimental results show that our method improves the recommendation performances over other methods.