Rome ….. Termini station, 2:00 pm on a Tuesday afternoon. Five young boys are standing next to the escalators, constantly shifting, dispersing, meeting up again. They are laughing, typing on their phones, chatting, smoking. They seem like average teenagers with fancy hairstyles and smart clothes. But every once in a while, they nervously glance over to the security personnel circling Termini station. Or carefully examine older men walking by.

While the world’s population of 7.4 billion is growing at 1.1 percent per year – about half the peak level of the late 1960s – enormous differences in demographic growth among countries are increasingly evident and of mounting concern to countries and the international community.