Introduction Despite the recent economic and financial crisis, global migration continues to rise. The estimated stock of international migrants amounts to more 230 million in 2013 according to figures of the United Nations (2013). Since the early 1990 the number of migrants worldwide increased by around 50 per cent. At present migrants represent about 3 per cent of total global population. Immigration becomes more important, especially in the ageing European economies that will experience a pronounced decline of the labour force due to demographic change. Moreover, Ozgen (2013) notes that migration is increasing in absolute scale but also in complexity in many parts of the world. As the composition of the migrant population is often very different from that of the country of destination immigration is usually accompanied by an increasing cultural diversity of the host society (Nijkamp 2012). Immigration and the growing cultural diversity of the population may have far-

reaching economic implications. However, the understanding of the effects of international labour mobility is still rather limited as emphasized by Zimmermann (2005) although the consequences of migration are an issue of research for a long time. And the public and scientific debate on the topic is rather controversial. A key question in this context refers to the economic costs and benefits for the receiving economies. Research on the economic consequences of migration has up to now focused on labour market effects and, more precisely, on the question whether immigrants depress wages and increase unemployment of native workers. Concerns about a possibly adverse impact of immigration on the labour market outcomes of the resident workforce are a main reason behind calls for more tight immigration policies in many highly developed countries. Economic theory provides some guidance on how immigration might impact

on the host economy. But the implications of theoretical models are not clear-cut. A considerable number of empirical studies deals with labour market effects of immigration. However, empirical evidence is also far from unambiguous. While some investigations point to a significant negative impact of immigration on labour market outcomes of native workers (e.g. Borjas 2003; Borjas and Katz 2007), the findings of other studies suggest that the influence is negligible (e.g.