The Learning by Doing Dimension of Extensive and Intensive Margins of Exports: the Case of Tunisia

The aim of this paper is twofold. The first consists in proposing the learning by doing approach as a theoretical background for which extensive and intensive margins of exports are jointly contributing to economic growth. The second is to verify if these margins are actual or not in Tunisia and if they are, as conjectured in this paper, a source of Gross Domestic Product expansion via a learning by-doing process. The two margins of exports are assessed thanks to an export differentiation index à la Hirshman-Herfindahl which is computed, by using three digit standard international trade classification (SITC) data. The learning by doing process associated to exports margins is approximated not only by weighting the export differentiation index by a scale variable capturing the experience increase but also by assessing the latter variable for the whole economy and for the manufacturing sector where the sophistication of goods favors learning by doing. A Vector Autoregressive model is applied on Tunisian time series data covering the period (1970-2016). Export differentiation indexes are computed for the manufactured exports (500-899 in SITC) and all exported goods (001-899). Both margins of exports are proved to sustain a learning by doing process by favoring from, one hand, an increase of experience of workers and, from the other hand, technological spillovers between goods of increasing sophistication. The two exports margins are not impacting growth positively unless they happen in the manufacturing sector. The diversification of manufactured exports after a given maturity in producing already exported products is the principal insight in term of political economy.