Which manufacturing firms learn by exporting?

Using a longitudinal database (1996--2003) at the plant level, this article analyses the causal nexus between international trade engagement and productivity in Portugal. By applying the propensity score matching and a differences-in-differences estimator, the learning-by-exporting hypothesis is analysed in particular. A higher growth of labour productivity and total factor productivity is found for new exporting firms. To uncover the channels through which the learning effects are driven, the same methodology is applied to some sub-samples. Learning effects are higher for new exporters that are also importers or start importing at the same time. Other factors affecting learning ability are found in firms exporting to more developed markets, in those that achieve a certain threshold of export intensity and mainly for those firms that belong to sectors where Portugal has a comparative disadvantage.