29 % of the population is less than 20 years of age
Today, Seine-Saint-Denis is the fourth largest county in Ile-de-France, Paris' region, in terms of it's population (preceded by Paris, Val d’Oise and Hauts-de-Seine), and the county with the second youngiest population of people aged 18-25 (preceded only by Paris).
The average population density in Seine-Saint-Denis is 5 875 habitants / km² as compared to 20 246 habitants/km² in Paris.