This NY Times article talks about the decline of Europe’s population:
To begin with, consider the extraordinary prospect of European demographic decline. A hundred years ago — when Europe’s surplus population was still crossing the oceans to populate America and Australasia — the countries that make up today’s European Union accounted for around 14 percent of the world’s population. Today that figure is down to around 6 percent, and by 2050, according to a United Nations forecast, it will be just over 4 percent. The decline is absolute as well as relative. Even allowing for immigration, the United Nations projects that the population of the current European Union members will fall by around 7.5million over the next 45 years. There has not been such a sustained reduction in the European population since the Black Death of the 14th century. (By contrast, the United States population is projected to grow by 44 percent between 2000 and 2050.)
Is Europe suffering from a memetic disease (the enlightenment?) or the demographic equivalent of old age?