The Jeunes and the Restless
This map represents six demographic trends in France, according to the Institut National de la Statistique et des Études Économiques. According to the report (pdf), young French men and women tend to flock to larger cities in their late teens and early twenties, usually for education, and return to their home towns and villages. What is more interesting is that in their mid-twenties to late thirties, when they search for permanent employment, they choose to go south and west (to either cities or suburbs.) Overall, the nation is shifting southward. The large, dark blue swath in the Northwest, where heavy industries once dominated, is a zone of negative migration: young people are leaving for the areas of high-tech industry. (Northern Alsace is almost an island in the deep blue sea, attracting both students and young people seeking employment.)
Paris, as to be expected, has its own characteristics. The spike in arrivals occurs at older ages than other large cities, and the departures occur much later. Where they really differ is in the ages in which migratory trends from the city becomes negative. In the large cities, students stay as long as they studies require, then leave. In Paris, young people stick around till their thirties, then leave. For the former, the age in which the population stabilizes (near zero departures by age) is in the mid twenties. For Paris, the numbers remain negative from the thirties until the seventies. This suggests that young people who move to Paris believe that they will be able to make a career and a home for themselves in the capital, but experience tremendous disappointment as they get older, leading to emigration of middle-aged Parisians. This may say something about the intensity of the Paris protests over the CPE in recent months. The Parisian youth sit at an intersection of hope and discontent, waiting for opportunity, but seeing people not much older than them give up for greener (or in this case, redder) pastures.
[Warning: I am colorblind, so don't be too harsh if I got the colors wrong.]
[ETA] The presence of tents around Paris is also an interesting trend.