Spain is one place where the need for workers is high — 24 million by 2050, according to the country’s central bank. But the backlash against a record number of migrants arriving clandestinely is also up. Spain’s prime minister has been visiting West African nations to shore up the fight against human smugglers, and trying to spread the recent arrivals around Spain equally, sometimes causing consternation. The World’s Gerry Hadden reports.