Talk:Zero population growth

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thread_title: Fair use rationale for Image:Pyat rublei 1997.jpg

message: What does this movie have to do with Zero Population Growth? It's not a movie about a society with zero population growth, it's a movie about a society in which there is no more children. That's not ZPG.--RLent (talk) 17:39, 9 April 2008 (UTC)
replies: text: Correct - zero growth is different from zero reproduction (which would result in rapid de-population).  ·:· Will Beback  ·:· 01:47, 10 April 2008 (UTC)
thread_title: [[Children of Men]]

message: zero poulation is the taking of humans and making them only have 2 kids per couple  —Preceding unsigned comment added by 67.172.242.254 (talk) 22:58, 23 September 2008 (UTC)
replies: text: Thats not true at all, ZPG has a much worse agenda than that. The fact of the matter is that peoples lifespans have been increasing for quite some time, and will continue to do so. For this reason alone, 2 per couple results in population growth.  —Preceding unsigned comment added by Zaphraud (talk • contribs) 03:24, 10 October 2008 (UTC)

text: Both of these comments are problematic. The birth rate to insure relacement is actually 2.1 children. Some people need to have more than two to make up for the fact that some couples have one or zero children, and some portion of that next generation will also not be fertile.  The current replacement rate is actually currently (in 2009) much lower than the needed replacement rate in some parts of the world ---especially first world countries. This is worsened by the fact that women in first world countries are having their chilren later in life. Simplistic solutions such as limiting the number of children to two are not feasible to maintaining populations. There are concerns that culture will be lost as certain ethnic, religious, or other groups attempt to enforce the 2 children or less rule in their population. —Preceding unsigned comment added by unsigned (talk 08:24, 15 January 2009 (UTC)
replies: text:  Presumably the birth rate to ensure replacement is 2 children on average - where the average is calculated over all "couples" including those who have zero children (including those who are infertile). Mitch Ames (talk) 13:25, 6 July 2009 (UTC)

text:  Negative population growth will most likely be required for many nations in order to avoid population collapses (starvation) because of exceeding biocapacity. List of countries_by ecological footprint 109.228.168.107 (talk) 23:37, 9 November 2012 (UTC)
thread_title:  zero poulation growth 

message: Because by definition a population is at equilibrium when its overall birth and death rates are equal, I changed the explanation to note the time lag in demographic transition theory is between the time when fertility (not birth) first drops to replacement level and the time when population levels off. "Birth rate" and "fertility" are very different terms although easily confused. The birth rate is how many babies born each year per 1000 people. The fertility is lifetime children per woman, usually determined by asking women of various ages whether they've had a child that year and taking a weighted sum. The section title should probably be "Relation between changes in fertility and population growth" or something like that. I may make the title change later when I can source the explanation. Ehrlich is good, but I need a source that defines "demographic equilibrium" explicitly as meaning the same thing as ZPG, and gives step-by-step general process explanations which Ehrlich omits. I will try to add this source next to Ehrlich.
The replacement level fertility has a complex mathematical definition and is recalculated every year, constantly changing along with the other rates. This means the explanation as I've expanded it still has subtle defects. For instance, I said, "even though fertility has dropped to replacement level" while ignoring that the replacement level isn't really constant. But including this extra detail will make the explanation cumbersome and impair the reader's grasp of it.
A link to the general "Demographics" article would help; I'm not sure how to format it yet. Unfortunately, however, that article, although it gives the basic equations, doesn't offer detailed process descriptions for demographic transitions either. It needs a section on the age structure of a population (those pyramid things), and would involve differential equations and integration if it were comprehensive. Jessegalebaker (talk) 03:17, 11 December 2015 (UTC)
thread_title: "Effects," section edited 11 Dec 2015

message: Is there a particular reason to bring Scalia into this? Did he rail against ZPG or something to make him the target of scrutiny?
(quote)  "For example, Antonin Scalia had nine children and if each of those had nine and if in each generation each offspring had nine, then in just 11 generations about 31 billion Scalias would live on the planet. That is the power of compound growth."  I like to saw logs! (talk) 15:28, 20 April 2016 (UTC)
thread_title:  How did [[Antonin Scalia]] get into this article? 

message: The sentence about Antonin Scalia is a (political) statement about Scalia which Frosty Wooldridge includes in his blog in "Church & State" with attribution to Jason Brent. (The link to it still works.) Unfortunately, nine raised to power 11 merely describes the optimal number of descendants Scalia might have after 11 generations if his progeny all prove similarly prolific. For growth of a human founder population, one must consider sexual reproduction with births given only by the women in the population. Which is why the United Nations UNDEP tracks the fertility rate, the number of children a woman expects to bear in her lifetime. The actual timing of the births matters as well; the population will grow faster if the women have their children while young, or grow more slowly if women delay having children.
Unfortunately Bartlett was a physics professor, not a demographer or actuary. His off-the-cuff exponential growth scenarios seem to have been cut out for the amusement of his audiences, especially students. Although he may have held pro-ZPG opinion; his material derives from a paper about energy use and the energy crisis he wrote in 1969, refined in 1978, and had converted into a speech he gave repeatedly to the end of his career.
Bartlett mainly discussed growth in fossil fuel consumption, not population itself, and omitted the mathematical treatment you need for a realistic model. This stuff isn't the best source for either demographics or ZPG, both difficult subject areas not at all accessible to non-specialists. This Wikipedia article is fatally flawed in my opinion and needs rewriting from scratch by a qualified person, which simply isn't going to happen. More Bartlett on energy use, see http://www.albartlett.org/articles/art_forgotten_fundamentals_overview.html
Jessegalebaker (talk) 13:24, 6 May 2016 (UTC)
thread_title:  Scalia 

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message: I believe this article should be expanded to include at least the related topics of stable population and stationary population. Does anyone agree? Miguelsxvi (talk) 12:07, 7 November 2022 (UTC)
thread_title:  Expanding this article 

message: Needs a section to cover the key criticisms of ZPG Newystats (talk) 09:00, 6 January 2023 (UTC)
thread_title:  Needs a criticisms section