مدل سازی سیاست های تجاری تحت ساختارهای بازار جایگزین

The paper focuses on the importance of assumptions made about market structure and firm behavior in empirical trade policy analysis. The contribution to the relevant literature is 3-fold: first the paper develops two original models which incorporate imperfectly competitive market structures in a spatial modeling framework; then it proposes a procedure to identify the degree of market power in international trading which is consistent with observed prices and traded quantities, and applies it to the banana market; finally, it assesses how analysis of the implications of recent changes in the EU import regimes for bananas (the Economic Partnership Agreements and the December 2009 WTO agreement) is affected by the assumptions made on the prevailing market structure.

Growing attention has been recently devoted to the role of intermediaries in international trade. Recent studies show that 24% of US imports are handled by “pure” intermediaries, that is, wholesalers and retailers, while on the export side they account for 11% of total trade (Bernard, Jensen, Redding, & Schott, 2010). The role of intermediaries has been highlighted also for Chilean imports – 35% are handled by wholesalers and 6% by retailers (Blum, Horstmann, & Claro, 2010) – and for China – 22% and 18% of total Chinese exports and imports, respectively, are handled by Chinese intermediaries (Ahn, Khandelwal, & Wei, 2010). Intermediaries are particularly important in several agricultural commodity markets, such as cereals, sugar, bananas and coffee, in which a small number of trading firms (not necessarily private) account for a large share of world trade and are, potentially, in the position to exert market power. These trading firms are, by and large, “pure” middlemen, that seldom produce themselves the products they trade. The aim of this paper is to address the relevance of the assumptions about market structure and trader behavior in empirical analyses of trade policies; in particular when studying trade policy issues concerning commodity markets in which traders play an important role, the assumption of perfect competition may be restrictive and policy prescriptions obtained based on this assumptions distorted. Yet, empirical trade policy analysis often relies on this very assumption (McCorriston, 2002). The paper analyzes recent changes in the European Union (EU) import regime for bananas, namely the Economic Partnership Agreements (EPAs) and the December 2009 WTO agreement which put end to the “banana war”. For several decades the EU import regime for bananas had been the cause of heated political confrontation, both domestically and internationally (Anania, 2006 and Josling and Taylor, 2003). The EPAs made EU banana imports originating from African, Caribbean and Pacific (ACP) countries duty- and quota-free (previously they were subject to a duty-free quota, with out-of-quota imports subject to the MFN tariff), while the WTO agreement called for a reduction of the EU MFN tariff on bananas. This case study is used to provide insights into the effects of assumptions on non-competitive behaviors by international traders in the evaluation of the impact of trade policies. In fact, the banana trade is among the most evident examples of high concentration in international markets, with three international trading firms accounting for over 65% of world trade. The EU Commission (EC, 2008 and EC, 2011) has found that five banana traders have violated EU rules on competition, and consequently imposed fines. Making different assumptions about market structure, the paper provides a quantitative assessment first of the impact of the trade preferences the EU granted ACP countries with the EPAs, and then of the erosion of these preferences resulting from the reduction of its MFN import tariff for bananas under the December 2009 WTO agreement. The banana market is possibly the one in which benefits from trade preferences granted by the EPAs and potential losses from preference erosion are the greatest (Alexandraki and Lankes, 2006, Low et al., 2009 and Yang, 2005). We use a single commodity, spatial, mathematical programming model. Compared to general equilibrium models, partial equilibrium models allow for a better representation of complex policy instruments, a more detailed representation of markets and require less restrictive assumptions. The choice of a spatial model – i.e., a model which is able to generate trade flows between each pair of countries – is due to the fact that it is particularly effective in representing policies where different regimes apply to imports from different sources, without having to impose at times questionable assumptions, such as imperfect substitution between goods produced in different countries (Armington, 1969). Current and previous EU trade regimes for bananas considered in this paper include preferential tariffs and tariff rate quotas (TRQs) applied on imports from specific groups of countries. The paper develops two modified versions of the Takayama and Judge (1971) spatial trade model representing imperfectly competitive market structures: the extreme case of international trading firms forming a cartel and the intermediate case of traders behaving as downstream oligopolists and upstream oligopsonists. A two step calibration procedure is used to make the models replicate observed trade data; this allows us to address a key issue, that is, which degrees of market power and which market structures are compatible with the observed data. This approach differs from those in the relevant literature. The degree of market power and market structure in an industry are estimated by means of econometric studies based on industrial economics models (Perloff, Karp, & Golan, 2007), while we use a calibration procedure. Following the pioneering work of Dixit (1988), calibration has been extensively used in empirical trade policy analysis to obtain the conjectural variation parameter, as a way to represent all market structures, from perfect competition to the pure monopoly case; however, notwithstanding its extensive use, concerns have been raised about the lack of theoretical foundations of the concept of conjectural variation (Helpmann and Krugman, 1989 and Vives, 2001). In this paper, we do not use conjectural variations; rather we address the issue of the market structure and the degree of market power by calibrating different models representing a range of market structures. Assumptions made on the market structure make the difference both in terms of the extent of the expected impact of a policy change and of its sign.1 With respect to the banana market, results show that observed data are not compatible with the existence of a cartel of international traders; in fact, observed traded quantities and prices are consistent with market structures with a relatively low degree of market power. The EPAs are expected to increase ACP exports to the EU by a considerable amount and generate consistent benefits for ACP countries, while the 2009 WTO agreement on bananas significantly reduces the preferential margin for ACP countries, but does not offset the benefits from the EPAs. One interesting finding is that, as the degree of market power increases, market structure becomes important not only in terms of the expected magnitude of the impact of policy changes, but in terms of its sign as well. The paper is organized as follows: the next section discusses the significance of imperfect competition for the banana industry, while Section 3 presents the model and Section 4 illustrates the calibration procedure used and the results obtained in terms of feasible market structures in the banana trade; Section 5 discusses the results of the policy analysis, while the final one offers concluding remarks.

The goal of this paper was to address the importance of the assumptions made about market structure and traders’ behavior in empirical trade policy analysis. We believe its contribution to unraveling this issue is 3-fold: it develops two original models which incorporate imperfectly competitive market structures in a spatial modeling framework; it proposes a procedure to assess the degree of market power in international markets which is applied to banana trade and, finally, it shows how the assessment of the effects of the most recent EU import regimes for bananas is affected by assumptions made on the prevailing market structure. The paper develops two modified versions of the Takayama and Judge (1971) spatial trade model. The first model includes a cartel of the firms handling international trade. The second model incorporates oligopolistic and oligopsonistic behaviors of trading firms through a mark-up; this modeling framework has the advantage of being flexible, easy to implement and does not require identification of conjectural variation parameters, which would imply making explicit assumptions about the number and symmetry of the firms exporting to each importing market. The percentage of mark-up provides a representation of the degree of market power without having to make restrictive assumptions about the nature of competition. The two step calibration procedure used to make the model replicate observed country net trade positions provides a useful tool to address an important issue for empirical policy analysis, that is: what is the range of degree of market power in the market under scrutiny? Reducing the space of the feasible market structures is relevant in assessing the effects of trade policy changes as these may crucially depend on assumptions made on the degree of market power exerted by relevant actors. Indeed, the result of the analysis presented in the paper for the banana market is that some of the market structures hypothesized turn out to be unfeasible, being largely inconsistent with observed traded quantities and border prices. This happens when a cartel maximizing firms’ joint profits is assumed, but also for imperfectly competitive world market structures where the mark-up is above 12%. In fact, the results show that observed data are only consistent with market behaviors which are far away from Cournot and, actually, are close to perfect competition under most values of demand elasticities and market shares. This result appears even more important given the high concentration of international trade of bananas. Regardless of the market structure considered, the implementation of the EPAs is expected to increase ACP exports to the EU significantly and generate overall consistent benefits for ACP countries; trade diversion occurs, with ACP exports previously directed to non-EU countries now redirected toward the latter. The 2009 WTO agreement significantly reduces the preferential margin for ACP countries, but does not offset the benefits from the EPAs; as a whole, with both the EPAs and the WTO agreement in place, ACP countries are better off in terms of both exports and export revenues. Analogously, despite the trade creation effect of the lower tariff they face on the EU market, the WTO agreement does not compensate MFN countries for the loss of competitiveness vis a vis ACP countries as a result of the EPAs. Because of the relatively low level of market power, simulation results are quite similar across the five market structures considered. However, the results show that as the feasible degree of market power increases, market structure matters not only in terms of the expected magnitude of the impact on the different agents involved, but in terms of its sign as well. The findings of this paper, and especially those concerning the degree of market power in the world market for bananas, depend upon a number of assumptions, common to most empirical studies on agricultural commodities, the most important of which are that: products are homogeneous; upstream and downstream firms have no market power; the policy changes considered have no effect on firm behavior or market structure. The removal of any of the above is likely to affect the results reached; however, this would imply the use of a completely different modeling framework and data needs which would be difficult to satisfy. Notwithstanding these simplifying assumptions, this paper proposes within a spatial framework an innovative and relatively simple procedure to assess the market power of intermediaries in empirical trade policy analysis; because of the importance of assumptions made regarding market structure in policy analysis, we believe that this approach could be useful to better evaluate the impact of trade policies.