The global media provide analyses of, in this case, rioting in France faster than the speed of thought, so Americans who may not know much about the social conditions of French cities encounter some strange certainties. Two of them are these: The pressure now being released by a young, partly immigrant underclass was decades in coming and based on housing, employment and cultural factors that have existed for generations; and, second, it’s been two weeks already, French leaders should have fixed the problem.

The parallel has been made of Paris to New Orleans; the riots are President Jacques Chirac’s Katrina response. True, it is a disaster to which the French government seemed too far removed and too slow to react. And it is interesting that in both cases, the response was a curfew so that anyone out at night might be arrested.

In this case, it seems, pre-emptive fighting makes sense.

Unlike the Gulf Coast storm, French rioters react to an official response, perhaps by making things worse. We don’t pretend to know how much police pressure the French should apply in this case or, as it appears, whether the uneven organization of these protests are causing them to fade even now. But it is apparent that young people with hope of a more prosperous future, with career and family plans and thoughts of leaving inadequate housing for something finer are not going to jeopardize all that for a chance to throw rocks at authorities.

The unemployment rate in France is around 10 percent; for those of African-Arab origin, it is 30 percent. The United States has much lower rates but, while it remains the land of opportunity, giving hope to millions, mobility here has stagnated. For income, at least, how much your parents make matters to your wealth as much now as it did 40 years ago and much more than was recognized in the past. That’s why when Congress finds exempting the first $8 million of someone’s estate unacceptably low and demands that all wealth escape what Republicans call the death tax, there is reason for concern.

This much is clear: When the levees broke in New Orleans, engineers in low-lying cities worldwide would have quietly double-checked the conditions of their own levees and counted Katrina as a reminder not to backslide and perhaps even to speed up their maintenance schedules. That works with the French riots too.