Learning from Trade Through Innovation: Causal Link Between Imports, Exports and Innovation in Spanish Microdata

The paper explores the learning from trade hypothesis. Standardized research approach searchs for learning effects from trade focusing solely on exports, whereby firm's learning effects are accounted in the firm of total factor productivity improvements. In contrast, this papers defines a firm learning from trade in tfirms of introduction of either new products or processes induced by its import and export links with foreign markets. By using microdata for a large sample of Spanish firms, including data on innovation and trade, we find clear sequencing between imports, exports and innovation. The results suggest that firms learn primarily from import links, which enables them to innovate products and processes and to dress up for starting to export. In a sequence, exporting may enable firms to introduce further innovations. These positive learning effects from trade, however, seem to be limited to small and partially medium firms only. On the other side, firms that are closer to the relevant technological frontier seem to benefit more from trading activities in tfirms of innovation than the technological laggard firms

Helicity-dependent cross sections for the photoproduction of π0\pi^0 pairs from nucleons

The double-polarization observable $E$ and helicity-dependent cross sections $\sigma_{1/2}$, $\sigma_{3/2}$ have been measured for the photoproduction of $\pi^0$ pairs off quasi-free protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost $4\pi$ covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the $\gamma N\rightarrow N\pi^0\pi^0$ reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrate the large impact of the new data.Comment: Submitted to Phys. Rev. Let