The paper explores the evolution of export diversification patterns along the economic development path. Using a large database with 156 countries over 19 years at the HS6 level of disaggregation (4'991 product lines) we look for action at the "intensive" and "extensive" margins (diversification of export values among active product lines and by addition of new product lines respectively) using various export concentration indices and the number of active export lines. We also look at new product introduction as an indicator of "export-entrepreneurship". We find a hump-shaped pattern of export diversification similar to what Imbs and Wacziarg (2003) found for production and employment. Diversification and subsequent re-concentration take place mostly along the extensive margin, although the intensive margin follows the same pattern. This hump-shaped pattern is consistent with the conjecture that countries travel across diversification cones, as discussed in Schott (2003Schott ( , 2004 and Xiang (2007).

This paper uses a gravity model to assess ex-post regional trade agreements. The model includes 130 countries and is estimated with panel data over the period . The introduction of the correct number of dummy variables allows for identification of Vinerian trade creation and trade diversion effects, while the estimation method takes into account the unobservable characteristics of each pairs of trade partner countries, the endogeneity of some of the explanatory variables as well as a potential selection bias. In contrast to previous estimates, results show that regional agreements have generated a significant increase in trade between members, often at the expense of the rest of the world. r 2004 Elsevier B.V. All rights reserved.JEL classification: F11; F15; C23

This paper reports panel gravity estimates of aggregate bilateral trade for 130 countries over the period 1962-96 in which the coe±cient of distance is allowed to change over time. In a standard speci¯cation in which transport costs are proxied by distance only, it is found paradoxically that the absolute value of the elasticity of bilateral trade to distance has been signi¯cantly increasing. The result is attributed to a relatively larger decline in costs independent of distance (such as handling) than in distance-related costs (e.g. oil price). An extended version of the model that controls for these two factors eliminates this positive trend without reversing it. However, when the sample is split into two groups (`rich-rich' and`poor-poor'), the paradox is maintained for the`poor-poor' group. While not conclusive, these results are consistent with the view that poor countries may have been marginalized by the current wave of globalization. Jel Classi¯cation: F12¤ Helpful comments from particpants at seminars at Cerdi and Wto are gratefully acknowledged. Agnµ es B ¶ enassy-Quere, Olivier Cadot, Paul Collier, Marcel Fafchamps, Maurice Schi®, Alan Winters gave helpful comments on an earlier draft.

This paper surveys the empirical literature on export and import diversification and its linkages with growth. We review widely used measures of diversification and the evidence about their evolution focusing on how export diversification relates to trade liberalization and economic development. We also discuss the linkages between trade diversification and productivity at the firm and industry level, highlighting new advances on the linkages between import diversification and productivity.