The article suggests a methodology to measure the intra-distribution dynamics of export specialization and applies it to a large set of countries in the last four decades. The article contributes to the literature on the dynamics of international trade specialization, making use of the information contained in the distribution of specialization indices, as initially suggested in Proudman and Redding (1997, 2000). In addition, the article makes use of conditional kernel densities and highest density regions to measure persistency/mobility in way that is applicable to other studies. Finally, the article empirically tests the determinants of specialization dynamics. The results reveal that there is considerable export specialization dynamics and heterogeneity across countries. In addition, it seems that the export specialization dynamics decelerated in most countries from 1967-1994 to 1980-2008 and there is a significant positive correlation between the indicators in the two periods. The econometric formulations reveal that higher human capital, improvement in infrastructures and macroeconomic stability seem to increase specialization dynamics.