where _xk,j_ are exports of a product _k_ to importer _j_ and _mj_ are imports by importer _j_ . (4) essentially captures the aggregate market penetration of exports, where markets are defined as all countries that import a given product. The primary advantage of this measure, relative to the geographic Herfindahl, is that it not only captures the distribution of exports across markets, but importantly normalizes this distribution by the potential markets that exist for these exports.

Table 4 reports the calculated export concentration measures for the period 2001-2007. We classify the indicators according to three dimensions: (a) diversification between different products across all exports; (b) diversification across exports within defined product groups; (c) diversification by geographic destination. The first column includes a count of the number of distinct products at the 4-digit HS level. The second and third columns contain the (normalized) Herfindahl-Hirschman and the Theil index. The fourth column reports the Theil (between) measure, in other words the between-section component of the Theil measure of overall diversification. The next three columns are analogous to the first three, but instead report median values for levels of diversification in the 21 HS sections for each measure. The eighth column reports the Theil (within) measure, in other words the within-section component of the Theil measure of overall diversification. The final three columns provide, in this order, a count of the number of distinct trading partners, the (normalized) geographic Herfindahl calculated by country share of total exports, and the export market penetration index.<sup>9</sup> Across all Syrian exports, there is a trend toward increasing diversification (columns 1–4). The Herfindahl index between all export lines has fallen significantly between 2001 and 2007, from a fairly concentrated 0.62 to 0.14, which is more consistent with moderate levels of diversification. This diversification trend is also broadly supported by the decomposed Theil (between) statistics, which illustrate a declining trend after 2003. By way of contrast, other economies in the region possess Herfindahls that range from well-diversified (Morocco, 0.03 and Lebanon, 0.03), to moderate diversification (Egypt, 0.14), to concentrated (Iran, 0.69 and Yemen, 0.72).<sup>10</sup> Seen another way, Syria has, over a seven-year period, moved from an export diversification structure consistent with oil-exporters to one more akin to non-oil exporters.<sup>11</sup> These changes in the extent of

> 9Notably, Table 4 leaves out one other (relatively) common measure of export diversification, the Gini index. We have chosen to do so for two main reasons. First, most of the dynamics of changes in export concentration are well captured by the other reported measures. Second, the main advantage to using a Gini index—its immutability under different sample sizes—is of less consequence in our case, where we are considering only one country with very limited changes in the availability of data.

> 10Since Herfindahls for the other economies are more stable over the period, these values are calculated as averages for the period 2001–2007, inclusive.

> 11Relative to other economies at a similar stage of development, however, Syria remains less diversified, in part due to its historical relationship with oil. For example, Honduras and Indonesia possess

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