The labor shortages are on both sides. However, the visa system in the US is horribly broken (http://www.overseas-exile.com/2013/04/whos-hiring-h1b-visa-w...). Further, with the introduction of the European Blue Card (http://www.overseas-exile.com/2011/02/european-blue-card.htm...), entry to Europe is getting easier and easier for skilled workers. Both sides have a labor shortage, but the US has traditionally had an advantage with one language and immigration law for 50 states. Now this is changing since Europe is starting to address the issue.