Water, power, and population
- Thread starter gar
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Barbqranch
Senior Member
- Location
- Arcata, CA
- Occupation
- Plant maintenance electrician Semi-retired
I believe the one child policy in China is being, or has been, phased out.
Not exactly. Couples can apply for permission to have more than one child.
gar
Senior Member
- Location
- Ann Arbor, Michigan
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- EE
161012-1835 EDT
Besoeker:
Consider a simplified model.
Assume the lifetime of everyone is 100 years, that males and females are each 50% of the population, and every female has one child. The population at the start of the program is 100 million. At 30 years of age each woman has their one child.
At the end of the first year of the program there are 99 million of the original group, there is a backlog of women from 0 to 30 years old that each will produce one child. Thus, the number of children produced per year will remain constant for 30 years. This number is 0.5 million. The net reduction in population for those 30 years is 1 - 0.5 or 0.5 million.
30 years after the start of the program the population is down to 100 - 15 or 85 million. After this period the reduction starts to increase.
There are some estimates that today 2.1 children per female are required for a stable population. This implies a good survival rate to childbearing age. Thousands or even hundreds of years ago that number would have been larger.
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Besoeker:
Consider a simplified model.
Assume the lifetime of everyone is 100 years, that males and females are each 50% of the population, and every female has one child. The population at the start of the program is 100 million. At 30 years of age each woman has their one child.
At the end of the first year of the program there are 99 million of the original group, there is a backlog of women from 0 to 30 years old that each will produce one child. Thus, the number of children produced per year will remain constant for 30 years. This number is 0.5 million. The net reduction in population for those 30 years is 1 - 0.5 or 0.5 million.
30 years after the start of the program the population is down to 100 - 15 or 85 million. After this period the reduction starts to increase.
There are some estimates that today 2.1 children per female are required for a stable population. This implies a good survival rate to childbearing age. Thousands or even hundreds of years ago that number would have been larger.
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drcampbell
Senior Member
- Location
- The Motor City, Michigan USA
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- Registered Professional Engineer
Um, no. The carboniferous period has ended. After white-rot fungi evolved, dead plants are consumed on the surface instead of being buried in deep strata that become coal & petroleum.
ggunn
PE (Electrical), NABCEP certified
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- Austin, TX, USA
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- Consulting Electrical Engineer - Photovoltaic Systems
You see? A divide by zero is MANY orders of magnitude.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
For a .33 policy
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
161013-1447 EDT
See https://en.wikipedia.org/wiki/Demographics_of_China . The graph does show a change in slope starting about 1995 to a slower growth rate. Birth rate exceeds death rate, but fertility rate is quite good, 1.55. So longevity is increasing faster than the reduction of children, but this won't last too long.
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See https://en.wikipedia.org/wiki/Demographics_of_China . The graph does show a change in slope starting about 1995 to a slower growth rate. Birth rate exceeds death rate, but fertility rate is quite good, 1.55. So longevity is increasing faster than the reduction of children, but this won't last too long.
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