A review of the past financial crises suggests that the 2008-2009 crisis could lead to a durable loss of activity. In the main scenario, the French economy might suffer a permanent loss of 7 points of GDP compared to the pre-crisis trend. The weakness of productivity is one of the mechanisms that could account for this permanent loss. This loss of productivity is related to the unexpectedly good performance of the French labour market during the crisis, regarding the loss of activity. The crisis has also accelerated the old tendency of debt increase the French economy has been facing for 30 years. At this point, the debt level becomes problematic.