The gravity model for international trade is one of the most successful empirical models in trade literature. There is a long tradition to log-linearise the multiplicative model and to estimate the parameters of interest by least squares. But this practice is inappropriate for several reasons. First of all, bilateral trade flows are frequently zero and disregarding countries that do not trade with each other produces biased results. Second, log-linearisation in the presence of heteroscedasticity leads to inconsistent estimates in general. In recent years, the Poisson gravity model along with pseudo maximum likelihood estimation methods have become popular as a way of dealing with such econometric issues as arise when dealing with origin-destination flows. But the standard Poisson model specification is vulnerable to problems of overdispersion and excess zero flows. To overcome these problems, this paper presents zero-inflated extensions of the Poisson and negative binomial specifications as viable alternatives to both the log-linear and the standard Poisson specifications of the gravity model. The performance of the alternative model specifications is assessed on a real world example, where more than half of country-level trade flows are zero. (authors' abstract) / Series: Working Papers in Regional Science

O objetivo deste trabalho é introduzir um método para a avaliação da viabilidade das exportações focando no crescimento econômico em termos de PIB do resto do mundo. Para isso são utilizados modelos locacionais e modelos de regressão baseados em modelos gravitacionais de comércio, ambos em conjunto. Este trabalho também apresenta de forma matemática e microeconômica a relação existente entre ambos os modelos. O estudo também testa o método introduzido por meio de um exemplo utilizando as exportações do complexo soja brasileiro entre 1996 e 2010. Os resultados obtidos não descartam o uso da metodologia proposta como instrumento de análise da viabilidade das exportações. / The aim of this work is to introduce a method for assessing the viability of exports focusing on economic growth of the rest of the world in terms of GDP. For this purpose, location models and regression models based on gravity models of trade are used together. This research also presents a mathematical explanation and the microeconomic relationship between both models. Also this work uses the example of Brazilian soybean complex exports between 1996 and 2010 to test the introduced method. The results do not rule out the use of the proposed methodology as a tool for analyzing the viability of exports.

This thesis provides an assessment of monetary integration in the West African Monetary Zone (WAMZ) focusing upon its feasibility and trade implications, in order to inform policy about the group’s deep integration scheme. The first aspect of the original contribution of the thesis focuses on one of the main issues in the debate of the monetary union in the WAMZ, namely the degree of asymmetry in macroeconomic shocks. The study examines the real effective exchange rate (REER) behaviour among the prospective candidates to assess the degree of potential costs of giving up monetary policy autonomy. The evidence reported from VECM, impulse response and variance decomposition analysis points to heterogeneous economies. Therefore, idiosyncratic shocks imply the need for different policy responses to adjust to macroeconomic shocks. The findings strengthen the case for policy autonomy in the region. The second aspect of original contribution of the thesis evaluates the potential effect of a common currency on trade among WAMZ member countries. Using the existing currency union in ECOWAS, the CFA franc zone, the chapter estimates the effect of a common currency on bilateral trade over the period 1980-2016 using the gravity model. The main conclusion reached is that membership of the CFA franc zone has promoted bilateral trade among members by 60%. The findings support the hypothesis that a common currency increases bilateral trade, which is a helpful guide for a WAMZ monetary union. In summary, the thesis demonstrates that in the long term, a common currency would promote intra-community trade, but at present, a monetary union is not feasible due to asymmetric macroeconomic shocks. Therefore WAMZ deep integration scheme would require members instituting adequate alternative adjustment mechanisms such as fiscal transfer schemes. / Ghana Education Trust Fund (GETFund) for the financial support and Division of Economics (now Accounting, Finance and Economics Group) for the offering of the Graduate Teaching Assistant Studentship

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