Davis agrees with Levy on the facts that the increased population in the world in the last two centuries is responsible for the rapid increase in the urban population. However, he notes that the birth rates and death rates in the urban centers are very low compared to the rate of increase in the urban population. He therefore concludes that rural to urban migration is the real course of the increased population in the cities.
In some modern cities, birth rate has been observed to be much lower compared to the birth rate which requires a higher number of immigrants to maintain the urban population. Despite the natural trends predicting a decrease, these cities have recorded progressive increase in population. This argument of increased rural to urban migration merges with Levy’s argument that industrial revolution, increased agricultural production and efficient means of transports have continuously forced people to migrate from the rural areas to the urban centers (Davis, pg 25).