I have two really quick comments.
One is that I don't think the tax had very much to do with it. A whole series of factors led to that growth of direct investment in Ireland. Among many others, they just got their timing right. It just happened to be at the time when these large high-tech U.S. firms were looking for a place to locate their firms in order to export in the EU. There was an English-speaking population, highly educated. Indeed, one of the cleverest things they did with those EU subsidies was to get rid of all tuitions for higher education. They had this very highly educated, low-wage workforce all ready for the big high-tech U.S. firms, so they located in Ireland in order to get into the EU. If it had happened at some other time, the effect would have been very different.
The second comment is that even if it did work, it only worked for one country. It's a beggar-thy-neighbour policy. What if every European country reduced their corporate taxes to 12%? What would be the effect? Zero. There's an enormous collective action problem with respect to corporate taxes. That's why the most you can advise a country is to keep its corporate taxes about in the middle of the pack and to try to negotiate with countries around the world not to try to beggar their neighbour in the way Ireland did. Why did Germany put up with it? In part they put up with it because Ireland was such a poor country at the time. There were just very unique circumstances that can never be duplicated.