Hierarchy construction schemes within the Scale set framework

Segmentation algorithms based on an energy minimisation framework often depend on a scale parameter which balances a fit to data and a regularising term. Irregular pyramids are defined as a stack of graphs successively reduced. Within this framework, the scale is often defined implicitly as the height in the pyramid. However, each level of an irregular pyramid can not usually be readily associated to the global optimum of an energy or a global criterion on the base level graph. This last drawback is addressed by the scale set framework designed by Guigues. The methods designed by this author allow to build a hierarchy and to design cuts within this hierarchy which globally minimise an energy. This paper studies the influence of the construction scheme of the initial hierarchy on the resulting optimal cuts. We propose one sequential and one parallel method with two variations within both. Our sequential methods provide partitions near the global optima while parallel methods require less execution times than the sequential method of Guigues even on sequential machines

Price Transmission in the Cocoa-Chocolate Chain

There is a common perception among consumers that the retail prices respond faster to an increase in the price of raw material than to a decrease. This paper aims at testing the existence of such asymmetric price transmission in the cocoa-chocolate chain on the French market. Two types of asymmetry are suspected: asymmetry in the transmission of positive and negative shocks that may reflect non-competitive behaviour in the chocolate industry and asymmetry in the transmission of small and large shocks that may be due do adjustment costs. These hypotheses are tested using the two-step approach to cointegration of Engle and Granger extended to encompass possible asymmetric adjustment to disequilibrium. Estimates indicate that a three-regime error correction model is the most appropriate. On the one hand, the chocolate price does not adjust to small shocks in the cocoa market. On the other hand, the speed of adjustment is larger for negative deviations than for positive ones. Les consommateurs ont souvent l’impression que les prix de détail répondent plus vite aux augmentations du prix de la matière première qu’aux baisses. Aussi, l’objectif de ce travail est de tester l’existence d’une transmission asymétrique des fluctuations de prix entre la matière première, la fève de cacao, et le produit fini, la tablette de chocolat sur le marché français. Deux formes d’asymétrie, ayant chacune une origine différente, sont recherchées : d’une part, une asymétrie dans la transmission des chocs positifs et négatifs, potentiellement liée à l’exercice d’un pouvoir de marché des industriels, et d’autre part, une asymétrie dans la transmission des grands et des petits chocs de prix liée à la présence de coûts d’ajustement. Les résultats, obtenus à partir d’une modélisation TAR du déséquilibre de prix par rapport à leur valeur de long terme, ne permettent pas de rejeter ces hypothèses. Sur la plus grande partie de la période couverte (1960-2003) le prix de la fève et le prix de la tablette évoluent indépendamment l’un de l’autre. Toutefois, au moment du boom du cacao (fin 70) le prix de la tablette répond rapidement à la hausse des cours de la fève tandis qu’à la fin des années 80, alors que le prix de la fève est retombé à un bas niveau, le prix de la tablette revient lentement vers l’équilibre.  modèle TAR, transmission de prix asymétrique, cacao

Price Transmission in the Cocoa-Chocolate Chain

There is a common perception among consumers that the retail prices respond faster to an increase in the price of raw material than to a decrease. This paper aims at testing the existence of such asymmetric price transmission in the cocoa-chocolate chain on the French market. Two types of asymmetry are suspected: asymmetry in the transmission of positive and negative shocks that may reflect non-competitive behaviour in the chocolate industry and asymmetry in the transmission of small and large shocks that may be due do adjustment costs. These hypotheses are tested using the two-step approach to cointegration of Engle and Granger extended to encompass possible asymmetric adjustment to disequilibrium. Estimates indicate that a three-regime error correction model is the most appropriate. On the one hand, the chocolate price does not adjust to small shocks in the cocoa market. On the other hand, the speed of adjustment is larger for negative deviations than for positive ones.modèle TAR;transmission de prix asymétrique;cacao

Are There Spillover Effects Between Coastal and Non-Coastal Regions in China ?

The evolution of regional policy between the Mao era and the Deng era generated much debate concerning inter-provincial disparities and the trade-off between efficiency and equity. The aim of this paper is to explore the existence of regional growth spillover effects looked for Deng’s policy. Indeed, the main objective was the spread of coastal provinces’ growth onto inland provinces’ growth. After reviewing the theoretical underpinnings of such effects, their existence is tested with panel data, for the period 1981-1998. Moreover, the hypothesis of an equal distribution of these effects over all the inland provinces is also tested. A relative failure to boost development of the western provinces from the coastal provinces’ growth is observed. Hence, it would seen to be an error to wait for spillover effects to be sufficient to reduce disparities between Chinese provinces in the short run.panel data., spillover effects, regions, growth, China

Japan's New Trade Policy:Good or Bad for ASEAN?

Because Japan is a primary investor and trading partner of all the troubled economies, in the midst of the crisis, Japan was called in to help the crisis-stricken countries by opening its market to cheaper imports from South East Asia. The article analyses the opening to trade of the Japanese economy with the help of a gravity equation on panel data using a Hausman-Taylor estimator. We show that there is no certainty that such a role, that is the opening of Japan, will have positive effects for the ASEAN countries, although no detrimental effects are expected. In the worst case scenario, this move and its impact on ASEAN countries would have neutral effect. This new Japanese policy, if applicable, appears to be not enough to (1) help ASEAN countries emerge from the financial crisis and (2) enable Japan to play the role it could and/or should in the region. Although many look at this solution – Japan opening its national market -- as the only one, on the contrary, Japanese help has been different and has proved to be very crucial to the ASEAN countries in need. In fact, the case of Malaysia is a good example of how Japan can help to foster the economy. Their experience shows that, next to trade ties, a greater emphasis can be put on a technical and/or other type of co-operation. Within this framework, Japan has helped Malaysia to recover faster from the crisis, without the former having to open wider its market to the latter. However, Japan is also driven by its own interests. Thus, if it wants to play a leading role in furthering ASEAN integration, especially in economic aspects, it will have to consider, soon or later, opening up its market to appear more reliable to its neighbours.Asian crisis – Hausman-Taylor – FDI, Gravity equation, Japan – ASEAN – Malaysia

International Integration of Chinese Regions and industrial location

This paper has two main objectives : first, to evaluate and to analyse the spatial concentration of industry in China; second, to estimate a link between the openness of China and this concentration. We are interested in the evolution of industrial location to study the regional specialisations. To explain increasing disparities we perform an econometric investigation, derived from the economic geography models, to test the impact of foreign trade on industrial location between the Chinese regions.China, regions, localisation, geographic economics

Geographical Spillovers and Growth

One of the main subjects in the theory of economic growth is to explain regional differences among rates of growth. In this paper, we address this issue through the notion of the "underdevelopment trap". Such a trap may be the result of strategic complementarities between investment decisions which generate multiple equilibria. The latter may be Pareto inefficient because of technological externalities. We test our model on international pooled data on the period 1970-90. The econometric analysis shows that economic growth rates depend on regional investment decisions. Moreover, it appears that such regional spillovers are channeled mainly through the physical rather than through the human capital stock.Underdevelopment Traps., Technological Externalities, Strategic Complementarity, growth, Regional Spillovers

IMF programs and tax effort What role for institutions in Africa?

When compared to other developing countries, most Sub-Saharan African countries are characterized by a disappointing level of development. Among the factors explaining this poor performance, the inadequate supply of public goods is often advocated. This inadequate supply is due either to poor efficiency of public expenditure, or to an insufficient tax effort. This paper is focused on this last factor. One of the reasons for the low level of public revenues could be the weak impact of the IMF programs on the tax effort. In the agreements that developing countries reach with the IMF, they commit to reduce their macro-economic imbalances, notably fiscal deficit, to a sustainable level. The measures necessary to achieve the overall budgetary objectives apply mainly to public expenditures as they are easy to reduce in the short term. However, the hypothesis of a positive effect of IMF programs must be considered: one objective of the African governments could be to maintain public expenditures at their previous level. To this end, African governments could choose to mobilize additional public revenues. Thus, most of IMF programs promote tax reforms leading to a more effective policy of public revenue mobilization. This last scenario of an increase of the level of public revenue is corroborated by the econometric analysis. The level of public revenue depends, among other factors, on the quality of institutions. However, the institutional quality of custom and tax administrations is weaker in Africa than elsewhere. This poor quality reduces the efficiency of IMF programs which may have a lower impact on the level of public revenue in African countries. These results point up two main lessons for the IMF (and more generally for lenders) and for recipient countries: 1) The role of technical assistance associated with the IMF programs is crucial, since it enables capacity reinforcement of the technical administrations in charge of the definition and implementation of the reform; 2) The technical assistance for tax and custom administrations must be strengthened for those countries which initially have a poor quality of bureaucracy.

IMF programs and tax effort What role for institutions in Africa?

When compared to other developing countries, most Sub-Saharan African countries are characterized by a disappointing level of development. Among the factors explaining this poor performance, the inadequate supply of public goods is often advocated. This inadequate supply is due either to poor efficiency of public expenditure, or to an insufficient tax effort. This paper is focused on this last factor. One of the reasons for the low level of public revenues could be the weak impact of the IMF programs on the tax effort. In the agreements that developing countries reach with the IMF, they commit to reduce their macro-economic imbalances, notably fiscal deficit, to a sustainable level. The measures necessary to achieve the overall budgetary objectives apply mainly to public expenditures as they are easy to reduce in the short term. However, the hypothesis of a positive effect of IMF programs must be considered: one objective of the African governments could be to maintain public expenditures at their previous level. To this end, African governments could choose to mobilize additional public revenues. Thus, most of IMF programs promote tax reforms leading to a more effective policy of public revenue mobilization. This last scenario of an increase of the level of public revenue is corroborated by the econometric analysis. The level of public revenue depends, among other factors, on the quality of institutions. However, the institutional quality of custom and tax administrations is weaker in Africa than elsewhere. This poor quality reduces the efficiency of IMF programs which may have a lower impact on the level of public revenue in African countries. These results point up two main lessons for the IMF (and more generally for lenders) and for recipient countries: 1) The role of technical assistance associated with the IMF programs is crucial, since it enables capacity reinforcement of the technical administrations in charge of the definition and implementation of the reform; 2) The technical assistance for tax and custom administrations must be strengthened for those countries which initially have a poor quality of bureaucracy.cerdi

How Instability Lowers African Growth

This paper aims to assess the role of instabilities on Africa low rates of growth during the seventies and eighties, using cross-section econometric estimates, on a sample of African and non African countries and two pooled decades. Africa exhibits higher "primary" instabilities (climatic, terms of trade and political instabilities), i.e. instabilities which are structural rather than the result of policy. These "primary" instabilities influence Africa growth, through a lower growth residual more than a lower average rate of investment. They do so by their impact on economic policy, which is evidenced by their influence on two "intermediate" instabilities, the instabilities of the rate of investment and of the real exchange rate, which significantly lower the rate of growth.