Talk:Life table

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Pearl Index is in the category of birth control, why not life table? I realize life tables are used for other purposes, too, while the Pearl Index is limited to birth control, but that's why articles are allowed to have multiple categories, right? Lyrl Talk Contribs 22:29, 20 July 2006 (UTC) ==4 aspects of life tables have errors:

1-the probability of surviving any particular year of age 2-remaining life expectancy for people at different ages 3-the proportion of the original birth cohort still alive 4-estimates of a cohort's longevity characteristics.

The table is actually a snapshot in of the present time. The prediction of life expectancy, Item 1 & 2, is predicated on conditions surrounding mortality remaining the same. Item 3, is simply wrong, as cumulative deaths, which is aggregated from cumulative survivors at a given age, actually are the sum of deaths at each period. They vary by all the conditions that affect mortality such as disease, nutrition and wars. These have varied over the course of the lifetimes listed, so the proportion of survivors at a given age is incorrect.

An illustration of this error is the recent death of the last WWI veteran, who died at 110. His cohort faced not only two world wars, but the influenza epidemic, and a long stretch of time with no antibiotics. So, while the table indicates 1 living person at his age of death out of 100,000, he was the only one who made it out of 2,000,000 troops of that war. This is consistent with my premise above. — Preceding unsigned comment added by Arodb (talk • contribs) 21:05, 7 March 2011 (UTC)

4 listed aspects of life tables (as follows) have errors:

 * 1-the probability of surviving any particular year of age
 * 2-remaining life expectancy for people at different ages
 * 3-the proportion of the original birth cohort still alive
 * 4-estimates of a cohort's longevity characteristics.

The table is actually a snapshot in of the present time. The prediction of life expectancy, Item 1 & 2, is predicated on conditions surrounding mortality remaining the same. Item 3, is simply wrong, as cumulative deaths, which is aggregated from cumulative survivors at a given age, actually are the sum of deaths at each period. They vary by all the conditions that affect mortality such as disease, nutrition and wars. These have varied over the course of the lifetimes listed, so the proportion of survivors at a given age is incorrect.

An illustration of this error is the recent death of the last WWI veteran, who died at 110. His cohort faced not only two world wars, but the influenza epidemic, and a long stretch of time with no antibiotics. So, while the table indicates 1 living person at his age of death out of 100,000, he was the only one who made it out of 2,000,000 troops of that war. This is consistent with my premise above. — Preceding unsigned comment added by Arodb (talk • contribs) 21:10, 7 March 2011 (UTC)

relevant topics ...
Hi there - I can see your concern, but let's look for a moment at what is going through a reader's mind when they are looking at the Life Tables article: they are reading about life tables, and related topics.

As it turns out, since life table techniques are used in birth control studies, there is indeed a link. And in that light I would be happy to put wikilinks around Pearl Index and Birth Control (which I will do in a minute). The link is then there for the reader to follow.

However, in relation to life tables, the "See also" section should be topics linked closely with life tables - not tangential topics. For example, would it be reasonable to include links to "Screwdriver" in each of the articles: Cars, Boats, Airplaces, Bicycles, Radios, Bookshleves, ... just because they use screwdrivers in manufacture & maintenance? I think not.


 * Life tables are (according to the article) used for insurance purposes (actuarial calculations), for some biology applications (population and actuarial calculations), and for some birth control applications. And nothing else.  This is a very limited number of uses, I would say all of these uses are linked closely with the topic of life tables.


 * The current categories are insurance, population, and actuarial science. It looks to me like one is missing.  I fail to see how 'population' is linked closely to life tables, while 'birth control' is not. Lyrl  Talk Contribs 00:04, 23 July 2006 (UTC)


 * I think you are misunderstanding the distinction between "life table" and "life table methods". I don't think life tables are used in any way for birth control studies.  However, the actuarial methods involved in the use of life tables would have general application to pregnancy and birth control studies, or indeed to any subject where you study a population which changes over time, and the members of the population move from one category to another (e.g., non-pregnant to pregnant for a birth control study, or from living to dead in the case of a life table).  So what I am saying is that life table "methods" are general methods and may have many applications, just as you mentioned regarding the screwdriver above.  However, life tables themselves, which represent the probability of death at various ages, don't have anything to do with pregnancy or birth control. -- Slowmover 16:24, 31 July 2006 (UTC)


 * I agree with Slowmover. You may wish to place the tag at life contingencies, but not here. -- Avi 16:32, 31 July 2006 (UTC)


 * You are right - I had not realized the distintion between life tables and life table methods. Does this apply to the biology section also, as that seems to be talking about birth rates as well as death rates/life expectancies? Lyrl  Talk Contribs 23:55, 31 July 2006 (UTC)
 * Well, the additional parameter for progeny does go beyond the purpose of a life table as it is used in insurance, which is my area of expertise. I have to plead ignorance as to how these tables are used by biologists, but a multi-parameter table involving progeny could be used in demographics to estimate future population, with decreases due to deaths and increases due to births, so it is a reasonable extension to the single-decrement life table, which is the most common type. Maybe that section could be expanded to include an example of a table using this parameter.  Anyway, it clearly belongs in a way that the birth control topic did not. -- Slowmover 14:43, 1 August 2006 (UTC)


 * I admit to not following all that, but I will defer to your greater knowledge. I would like to have discussion of the life-table methods used for birth control studies somewhere, however - would the life contingencies name be most appropriate?  Or life table methods? Lyrl  Talk Contribs 17:10, 1 August 2006 (UTC)
 * "Life contingencies" is a more general term than "life table methods", but since both of those are red links, I'm not sure where they are in Wikipedia. I spend most of my time on WP on other interests, not insurance/reinsurance, although I may devote more time to it, since some of the content is biased towards specific areas of practice. There are many actuaries editing on WP, and I would direct the question to one of them, such as User:Avraham, since they are probably more familiar with how the WP material has been organized. -- Slowmover 20:48, 1 August 2006 (UTC)

I'm actually a casualty actuary, not a life actuary, although our initial training is the same. Life contingencies includes the study of mortality, and using life tables, although to be very picky, it may be more restricted to the study of the time-value of money adjusted for mortality uncertainty. I'd suggest dropping a line on user:josephbrophy's page, he is a retired life actuary and would likely be able to give you even better guidance. There really is no good article for "life table methods" now, that is something that would be in a lifecon article. Maybe something in category:demographics is more appropriate? -- Avi 20:54, 1 August 2006 (UTC)

Question about the math
It would be helpful if someone could explain all of the columns in the CDC Table 1., since that is presented as a model life table. Specifically I mean L(x) and T(x)dealing with person-years lived. I would try but don't know how to use math notation on Wikipedia.--Chinawhitecotton 23:23, 21 January 2007 (UTC)

Survivorship curves
Survivorship curves are closely related to life tables, being more or less a graphical form of them. They seem to be used more exclusively in population ecology than in more anthropic fields though. I suppose the subject should probably have its own article? (it's either that or cover them here and/or in the population ecology article itself) Richard001 (talk) 08:27, 26 March 2008 (UTC)

Definition
Statistics of life expectancies; used as basis for life insurance costs.

Period vs. Cohort
Can someone who is competent in this subject put in a brief explanation of the distinction between a period table and a cohort table? —Preceding unsigned comment added by 65.217.188.20 (talk) 14:26, 27 January 2009 (UTC)

Period, Cohort AND Projected (= Dynamic)(= Prospective) Life Tables
There exists another type of life table, i.e. projected life tables. Farily recent development. See e.g. http://www.cmap.polytechnique.fr/~hillaire/SurveyLongevite.pdf. Projected life tables anticipate to the (most likely) evolution of human mortality. They have 2 entries: age and calendar year. For each age, the probability of dying at that particular age, during a particular year, t, is given by $$q_x(t)$$ or $$q_{x,t}$$. This solves the drawback of period life tables where generations are mixed and demographic indicators (such as expected lifetime) do not correspond to one particular generation. — Preceding unsigned comment added by 193.190.253.147 (talk) 14:56, 16 June 2014 (UTC)

by occupation
article needs a reference to tables by occupation — Preceding unsigned comment added by 122.61.61.161 (talk) 06:51, 7 August 2012 (UTC)

"An actual population from the present" - Not necessarily!
Life tables are important in historical demography, too, and this isn't always directly derived from present populations. For example, Coale and Demeny derive some of their model life tables from recent data, but derive the lower life expectancy versions from mathematical adjustment to the better-documented higher life expectency versions. Woods derives his model life tables from early twentieth-century Chilean data, which may be recent, but not present. Other attempts have used Egyptian records, Ulpian's figures, etc. for adult mortality, with other estimates for child mortality. Saskia Hin goes over some of this in The Demography of Roman Italy.108.56.154.33 (talk) 23:46, 7 March 2015 (UTC)

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