According to trackaah.com, the average density of the French population, 74 residents per sq. km. (1926), is the result of very different values. There are various causes of these differences, but in any case we can refer to certain general principles. The highest densities are found in urban and industrial regions, where only a constant increase is noted. The average densities are typical of the most fertile rural regions and especially those where once there was some industry (home weaving, small metallurgy, woodworking, etc.): in these regions the increase in the agricultural population has ceased, and the decrease it is often due to the disappearance of rural industries. The cultivation of cereals, even in the fertile plains, brings with it a relatively low population density, much lower than the average in France: this is especially noticeable in the Beauce. The cultivation of the vine, on the other hand, always carries relatively strong densities (côtes della Sciampagna, Burgundian Gold Coast and also the lowlands of the lower Languedoc); and the same can be said for the cultivation of vegetables and early fruits (Rhone valley, Brittany, etc.). Although it is not possible to establish the maxim that there is a constant relationship between the value of the land and the density of the population, nevertheless the villages of small properties are almost always more populated than those of large properties. The minimum densities are found in forest regions, which may also have a certain extent in the plains (eastern part of the Paris Basin, Gascony moors), but which generally occupy a greater surface area in the mountains (Alps, Jura, Vosges); and they are also found in regions with uncovered but absolutely sterile soil (savartsof Champagne). It goes without saying that the alpine area in the higher parts is depopulated and the subalpine area is largely sparsely inhabited.
The highest densities (see map) are found in the north of France and especially in the departments bordering Belgium: Nord (341), Pas-de-Calais (174). The presence of the most important French coal basin, giving rise to various industries, led to the intense renting of the population in this area but the population was very significant even before, due to the fact that, before the nineteenth century, a rational agriculture it was already coupled with some industries widespread in the countryside. Another dark spot marks Lower Normandy on the map (Lower Seine, 140); here too they are ancient rural industries (textiles), which are now concentrated around some cities, Rouen, Elboeuf, etc.: the presence of two of the largest ports in France (Le Havre and Rouen) favors their activity. The surroundings of Paris have, of course, a very dense population, and the maquis extends more and more, going up the valley of the Oise as far as Creil. Alsace has long been a very populated region; despite the existence of large forests, the average of the Bas-Rhin department reaches 191 residents per sq.km .; but at the foot of the Vosges there is the maximum density (250 and 300 residents per sq. km.) due to the vineyards and the large number of small industrial centers; this area extends through the Burgundy Gate towards Franche-Comté, throughout the cotton and metallurgical region of Belfort and Montbéliard, as far as Besançon. Brittany, although generally having a rather poor soil, is one of the most populated regions; but the strong densities are all confined to the coast (200 and in some points 250 residents per sq. km.), where are the best soils, with crops of first fruits, and almost all cities (fishing ports or commercial ports). The center and the south of France have very rare areas with a high density; some of them are due to the presence of coalfields, which, although less important than those in the north, have determined the development of large-scale industry (Le Creusot, Saint-Étienne). In Aquitaine, the Garonne valley, because of its fertility and its function as a trade route, contains numerous cities and large villages, which are dedicated to rich crops: vineyards, fruit trees and first fruits: the density is therefore considerable. The wine-growing plain of Lower Languedoc also has an above average density (100). The Saone-Rhône corridor, although of great commercial importance, is not all very populated: here the most extensive dark spot on the map is that due to the presence of Lyon, which is linked to the other of the coal basin of Saint-Étienne, and which, due to the ancient industries scattered here and there in this region, penetrates into the lower Dauphiné, thus reaching Grésivaudan, the only one of the great Alpine valleys that has densities over 100 residents. Another region with a high density and constant increase in population is the irrigated plain of Comtat (Avignon, Cavaillon, etc.). The surroundings of Marseille and Nice present the last areas with intense population.
The regions with the lowest density are not lacking even in the north of France: Champagne Pouilleuse with its savartsit is very depopulated (less than 20 residents per sq. km.), and the high Burgundian plateaus (Châtillonnais, plateau of Langres), covered with large forests, have low densities, which are continuously decreasing, as the iron industry has completely disappeared, once a source of some prosperity. This area joins the great forests of Lorraine. The Massif Central is very sparsely populated above 700 and 800 m. (high Limousin, high Cantal, Margeride and Aubrac, high Velay, high Vivarais). In Aquitaine, the Gascony moors have always been almost a desert. The rational exploitation of the pine forests has enriched the rare villages, without causing a notable increase in population (Landes, 28 residents per sq. Km.). The Alps are not as deserted as their heights would suggest.
Most of the wide valleys of the Savoy and the Dauphiné have areas with densities above the average of France, which push forward between the solitudes of the upper subalpine area and the alpine area itself. On the other hand, the Alpes de Provence are almost completely abandoned by men: deforestation has ruined the soil on the slopes: in a century, the relative population of some districts has been reduced by half, reaching less than 10 residents. per sq. km.