This chapter looks at how the prosperity gap between the member states is affected by the free movement of workers within the EU. One key purpose of free movement is to even out economic imbalances between the member states. The author’s analysis shows that labour mobility within the Union is too limited to make any significant contribution to economic equalization between the member states. However, mobility still has positive effects in terms of the income gain it implies for the migrants themselves and by helping to reduce labour shortages in specific sectors in specific countries. Contrary to common belief, moreover, migrants contribute somewhat more to the public purse than they cost. The author concludes that the Union and its member states should strive to uphold the free movement of labour, although it has never been as questioned as it is today.