cities as population sinks

This is an answer to Sydney, who posted this comment on one of my previous posts. I'm not reacting to Sydney's post per se (i am very thankful for his kudos) but to a sentiment he expressed that I think is shared by a lot of pinoys. Sydney said:

"There is a lot of work to do in MM. There are some improvements going on but maybe it is too little too late especially with the ever growing population."

I looked through the population stats for Metro Manila (from the 2000 census) and it looks like, although the population is still growing, it is growing at a slower rate.

This corresponds to both Phillip Longman's and Stewart Brand's findings that cities are population sinks. Fertility drops when countries urbanize -as people who move to cities have less children -the rate drops below 2.1% (the replenishment rate). Most city growth in the next 50 years will be driven by in-migration. (Which is a perfect segue to what will be my next post: on Subic as a metropolis).


ed said...

"Fertility drops when countries urbanize--as people who move to cities have less children..."

Does this still apply to people who have already moved in, specifically, the urban poor, whose growth rate seems to be the driving force behind Manila's population? Are they having less children?

I haven't listend to the lectures yet so I hope you don't mind this question here. Thanks.

Urbano dela Cruz said...

Yes. It takes about a half a generation for the drop to occur. But invariably city dwellers have lower fertility rates. (Women are too busy making a living to have more babies.)

"The continuing urbanization trend has had perhaps the largest impact on the fall of fertility rates and population growth. Cities are population sinks primarily due to their tendency to diminish the utility of children -- while children are an asset in rural areas, they are a liability in the city -- and to increase levels of education among women. Educated women tend to get married later in life and have fewer children. Today average age for marriage for women is 23 and 27 for men. "

Sidney said...

Indeed those are interesting figures. I just wonder if they take into account the trend of migration from village to city.

The Philippines is still very centralized and as such a pole of attraction for the rest of the country.

There seems to be other statistics around telling another story.
MM in 1995 at 9.29 million and MM in 2015 at 14.66 million. Which is a steep increase in population.

The world's urban population is currently growing at four times the rate of the rural population Between 1990 and 2025, the number of people living in urban areas is projected to double to more than 5 billion; if it does, then almost two thirds of the world's population will be living in towns and cities. An estimated 90 percent of the increase will occur in developing countries.

Source:World Resources Institute.

But I am not familiar with the topic and you might be right or people read/interpret the statistics differently.

Sidney said...

And to put every statistic in doubt :-)

How accurate are projections of future city sizes?
Efforts to predict the size of cities have proven less accurate than projections of national and regional populations. While the world's total urban population has been projected with some accuracy, projections of individual cities' populations and of cities' relative sizes have been much less reliable.

These shortcomings are partly due to the incompleteness of census information prior to the 1980s. But they also reflect the complexity of urban population dynamics. Like national populations, the size of cities depends on fertility, mortality and external migration rates, but it also depends on the differentials between urban and rural fertility and mortality and on migration within countries. Population movements are far more sensitive to regional variations in economic opportunities than are fertility and mortality.

It is also hard to predict changes in the spatial dimension of urban systems. In some cases, the population becomes increasingly less concentrated in central cities and more dispersed into urban systems of varying size with different economic specializations. Such patterns are difficult to predict.

In São Paulo, for example, the 1991 census showed both the population and the growth rate to be much smaller than anticipated. This reflected a large net outmigration, partly due to the relocation of industry to smaller cities, and a lower than expected fertility level.

Other unanticipated economic developments have upset expectations more dramatically. In 1982, Shanghai was the only Chinese city that the United Nations projected to be among the world's 20 largest urban centres in the year 2000, with an expected population of 13.5 million. By 1994, however, Shanghai, Beijing and Tianjin were all projected to be in the top 12 by 2000 (all three are currently in the top 15) and Shanghai's projected population has grown to 17.2 million.

The unreliability of forecasting is clearest in regard to single cities. Of the cities projected in 1982 to be the 15 largest in 2000, the total population was expected to be 233.8 million. This is close to the 1994 projection of 230.1 million in the top 15 cities in 2000.

However, the lists are not the same; the 15 cities in the 1982 list are currently projected to total 215 million people by 2000 – 18 million below the 1982 projection. Some cities were very poorly estimated. The current projection for Tokyo in 2000 is 10.8 million people larger than was projected in 1982; Mexico City's population in 2000 is now expected to be 9.9 million smaller than was projected in 1982.


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