INFLUENCE OF INDUSTRIAL DEVELOPMENT 345 



rapidly than the inferior ones, and do they attract the better or 

 the poorer stocks from the surrounding country? 



Probably the treatment of these questions which has suc- 

 ceeded in arousing the most discussion in Hansen's work Die 

 drei Bevolkerungsstufen. Hansen divides the population into 

 three classes: (i) the landowners from nobles owning estates to 

 the peasants with small holdings, (2) the middle class consisting 

 of officials, professionals, artisans, merchants, and (3) the prole- 

 tariat and day laborers and people in general with scanty means 

 of subsistence. Needless to say these are not well-defined groups 

 and that there is a continual transfer from one group to another. 

 The first class, the country dwellers, according to Hansen, con- 

 stitute a large proportion of the rural contribution to the city 

 population. It is this class that has the highest birth rate. Their 

 surplus as a result of economic pressure flows to the cities where 

 it supplies the second class with most of its members. Here they 

 are subjected to conditions of life which enhance the death rate 

 and reduce the birth rate so that, notwithstanding the superior 

 economic status which they acquire, they rapidly diminish in 

 number. Urban immigrants, according to Hansen, are of better 

 average quality than those who remain to carry on agricultural 

 pursuits. It is this rural influx that keeps up the vitality of urban 

 populations, and is mainly responsible for urban growth. Many 

 cities, were they dependent upon natural increase alone, would 

 suffer an actual loss of population. Dr. Boeckh has estimated 

 that the fertility of the city born in Berlin is not high enough to 

 perpetuate the stock. Paris for a long time has not been self- 

 sustaining. Lagneau calculated that were it not for immigration 

 its population would decrease 50 per cent in each generation. 

 Where cities grow through their own birth rate their increase is 

 dependent upon the fertility of the proletariat, since the middle 

 class is generally not self-perpetuating. Between the recruits 

 coming from other classes and its own fecundity the third stratum 

 perpetuates itself even under the unfavorable conditions into 

 which it is forced through economic pressure. But through 

 overcrowding, poor food and other destructive agencies, it tends, 



