On the Star Class Group of a Pullback

For the domain $R$ arising from the construction $T, M,D$, we relate the star class groups of $R$ to those of $T$ and $D$. More precisely, let $T$ be an integral domain, $M$ a nonzero maximal ideal of $T$, $D$ a proper subring of $k:=T/M$, $\phi: T\to k$ the natural projection, and let $R={\phi}^{-1}(D)$. For each star operation $\ast$ on $R$, we define the star operation $\ast_\phi$ on $D$, i.e., the ``projection'' of $\ast$ under $\phi$, and the star operation ${(\ast)}_{_{T}}$ on $T$, i.e., the ``extension'' of $\ast$ to $T$. Then we show that, under a mild hypothesis on the group of units of $T$, if $\ast$ is a star operation of finite type, 0\to \Cl^{\ast_{\phi}}(D) \to \Cl^\ast(R) \to \Cl^{{(\ast)}_{_{T}}}(T)\to 0 is split exact. In particular, when $\ast = t_{R}$, we deduce that the sequence 0\to \Cl^{t_{D}}(D) {\to} \Cl^{t_{R}}(R) {\to}\Cl^{(t_{R})_{_{T}}}(T) \to 0 is split exact. The relation between ${(t_{R})_{_{T}}}$ and $t_{T}$ (and between \Cl^{(t_{R})_{_{T}}}(T) and \Cl^{t_{T}}(T)) is also investigated.Comment: J. Algebra (to appear

Learning-by-exporting in Korean Manufacturing: A Plant-level Analysis

The paper analyzes whether firms that start exporting become more productive utilizing recently developed sample matching procedures to control the problems from self-selection into the export market. We use plant level panel data on Korean manufacturing sector from 1990 to 1998. We find clear and robust empirical evidence in favor of the learning-by-exporting effect; total factor productivity differentials between exporters and their domestic counterparts arises and widens during several years after export market entry. We also find that the effect is more pronounced for firms that have higher skill-intensity, higher share of exports in production, and are small in size. Overall, the evidence suggests that exporting is one important channel through which domestic firms acquire accesses to advanced knowledge and better technology. Also, the stronger learning-by-doing effect for firms with higher skill-intensity seems to support the view that gabsorptive capacityh matters to receive knowledge spillovers from exporting activity.Learning-by-exporting, Productivity, Propensity score matching