Do native predators feed on non-native prey? The case of round goby in a fluvial piscivorous fish assemblage

We evaluated whether or not the invasive round goby (Neogobius melanostomus) represents an important prey source for seven native fish predators in Lake St. Pierre (St. Lawrence River, Canada). The frequency of occurrence of round goby in the stomach contents of brown bullhead (Ameiurus nebulosus) and channel catfish (Ictalurus punctatus) was very low (< 5%), while for the five other predators, it varied between 22% (yellow perch; Perca flavescens) and 65% (sauger; Sander canadensis). Several competing models linking the probability of occurrence of round goby in stomach contents to variables related to space, physical habitat, biotic interactions and predator size were tested for the five species feeding on round goby. Results indicated that space variables influenced round goby occurrence in stomachs for all species. In addition, physical habitat variables had an influence for sauger and walleye (Sander vitreus); biotic variables had an influence for yellow perch, walleye and sauger; and size had an influence for northern pike (Esox lucius), smallmouth bass (Micropterus dolomieu) and walleye. These results are discussed in light of known biological features of the round goby and native predators studied here and have important implications in terms of understanding round goby invasion success in the Great Lakes–St. Lawrence system.     

Pareto-Improving Social Security Reform

It is generally accepted that moving from an unfunded to a funded social security system implies a welfare loss for the transition generation—that is, the generation that has to pay twice: first, saving for its own retirement and, second, contributing to the pensions of the then retired generation. This article shows that in a setting of endogenous growth with positive externality such a transition can be Pareto improving. But it argues also that social security reform is more a pretext than a requirement for internalizing such a positive externality.     

On the generic inefficiency of differentiable market games

It is shown that a differentiable market game remains generically inefficient when its strategic outcome function is perturbed smoothly. The proof is based on Thom's transversality theorem and removes any restriction regarding the dimension of the strategy spaces. A converse result is that almost all efficient market games that are competitive are characterized by Bertrand-like non-differentiabilities. Finally a synthesis between the Cournot-and-Bertrand-type approaches to Walrasian equilibrium, as recently developed in the literature, is suggested.     

Productivity, terms of trade and the ‘home market effect’

This paper analyzes the international transmission and welfare implications of productivity gains and changes in market size when macroeconomic adjustment occurs both along the intensive margin of trade (changes in the relative price of existing varieties of tradable goods) and the extensive margin (creation and destruction of varieties). We draw a distinction between productivity gains that enhance manufacturing efficiency and gains that lower the cost of firms' entry and of product differentiation. Countries with lower manufacturing costs have higher GDP but supply their products at lower international prices. Instead, countries with lower entry costs supply a larger array of goods at improved terms of trade. Output growth driven by demographic expansions, as well as government spending, is associated with an improvement in international relative prices and firms' entry. While trade liberalization may result in a smaller array of goods available to consumers, efficiency gains from deeper economic integration benefit consumers via lower goods prices. The international transmission mechanism and the welfare spillovers vary under different asset market structures, depending on trade costs, the elasticity of labor supply, and consumers' taste for varieties.     

Preferential Rules of Origin and the Multilateral Trading System: Pro-Development Policy Options

With the proliferation of regional trade agreements since the late 1980s and early 1990s, preferential rules of origin have also proliferated. The discussion on these rules has gradually shifted from a purely technical discussion (“how to establish the origin of goods not wholly obtained in one country”, and hence, “how to apply trade preferences in these cases”) to a wider discussion also touching upon the transaction costs caused by having a “spaghetti bowl” of rules, and the actual or presumed neo-protectionist use that is being made of them. In the context of the discussion on possible policy options for developing countries simultaneously involved in (or negotiating) regional and multilateral trade agreements, this article will first give a brief overview of the findings of the recent empirical literature. Some indications are then presented as to what such policy options could look like. This paper was first presented at the Ad-hoc Expert Group Meeting on The Development Interface between the Multilateral Trading System and Regional Trade Agreements, Session III Regulatory Provisions in RTAs, Palais des Nations, Geneva, 15-16 March 2007. It is partly based on P. De Lombaerde, L. J. Garay : Preferential Rules of Origin: EU and NAFTA Regulatory Models and the WTO, in: The Journal of World Investment & Trade, Vol. 6, No. 6, 2005, pp. 953-994; and L. J. Garay, P. De Lombaerde: Preferential Rules of Origin: Models and Levels of Rulemaking, in: S. Woolcock (ed.): Trade and Investment Rulemaking: The Role of Regional and Bilateral Agreements, Tokyo 2006, UNU Press, pp. 78-106.     

Weather Index Drought Insurance: An Ex Ante Evaluation for Millet Growers in Niger

In the Sudano-Sahelian region, which includes South Niger, the inter-annual variability of the rainy season is high and irrigation is limited. As a consequence, bad rainy seasons have a massive impact on crop yield and regularly result in food crises. Traditional insurance policies based on crop damage assessment are not available because of asymmetric information and high transaction costs compared to the value of production. We assess the risk mitigation capacity of an alternative form of insurance which has been implemented at a large scale in India since 2003: insurance based on a weather index. We compare the efficiency of various weather indices to increase the expected utility of a representative risk-averse farmer. We show the importance of using plot-level yield data rather than village averages, which bias results due to the presence of idiosyncratic shocks. We also illustrate the need for out-of-sample estimations in order to avoid overfitting. Even with the appropriate index and assuming substantial risk aversion, we find a limited gain of implementing insurance, which roughly corresponds to, or slightly exceeds, the cost observed in India for implementing such insurance policies. However, when we separately treat the plots with and without fertilisers separately, we see that the benefit of insurance is slightly higher in the former case. This suggests that insurance policies may slightly increase the use of risk-increasing inputs such as fertilisers and improved cultivars, and hence improve average yields, which remain very low in the region.