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==Demography==

==Demography==

In [[Demography]], fertility is the statistical analysis of having babies.  Couples do it, and so too do entire societies, in a way. Therefore demographers approach the topic at both the individual and the social level. At the individual level, the statistics are normally analyzed in terms of the mother, though admittedly the father plays a role as well. At the social level we measure fertility with different rates using birth statistics and census data. Research on fertility inside the United States has slowed in recent decades, because most of the important questions have been answered. nearly identical. There has been a shift from a focus on fertility as the basis of population growth to one of fertility as a component of health, marital and family-building patterns, and the connection to women's employment and careerism. There has been new attention to racial and ethnic patterns, and to the fertility of unmarried women. Attention has shifted to historical patterns in the US and Europe, going back to the year 1600. Even more important, attention has shifted to the rapid growth of population in developing countries, especially in Asia, Africa and Latin America. In terms of world population, the main issue is the overall number of births, and how it can be reduced.  

In [[Demography]], fertility is the statistical analysis of having babies.  Couples do it, and so too do entire societies, in a way. Therefore demographers approach the topic at both the individual and the social level. At the individual level, the statistics are normally analyzed in terms of the mother, though admittedly the father plays a role as well. At the social level we measure fertility with different rates using birth statistics and census data. Research on fertility inside the United States has slowed in recent decades, because most of the important questions have been answered. nearly identical. There has been a shift from a focus on fertility as the basis of population growth to one of fertility as a component of health, marital and family-building patterns, and the connection to women's employment and careerism. There has been new attention to racial and ethnic patterns, and to the fertility of unmarried women. Attention has shifted to historical patterns in the US and Europe, going back to the year 1600. Even more important, attention has shifted to the rapid growth of population in developing countries, especially in Asia, Africa and Latin America. In terms of world population, the main issue is the overall number of births, and how it can be reduced.  

==Measuring Fertility==

==Measuring Fertility==

The most basic measurement of fertility is the number of births; combined with deaths and migration, it permits the calculation of population change. To compare countries or groups, we must relate the number of births to the total population ("crude" birth rate) or to the number of women at risk (various measures.)   

The most basic measurement of fertility is the number of births; combined with deaths and migration, it permits the calculation of population change. To compare countries or groups, we must relate the number of births to the total population ("crude" birth rate) or to the number of women at risk (various measures.)   

===Period Measures===

===Period Measures===

"Period" measures refer to a cross-section of the population in one year. "Cohort" data on the other hand, follows the same people over a period of decades. Both period and cohort measures are widely used.   

"Period" measures refer to a cross-section of the population in one year. "Cohort" data on the other hand, follows the same people over a period of decades. Both period and cohort measures are widely used.   

===Biological Determinants.===

===Biological Determinants.===

"Fecundity" is the biological ability to have children, It is a function of age, health and nutrition. Fecundity begins at menarche, is low for several years and then increases quickly to a maximum in the early 20s, then declines to menopause (about age 50). "Natural fertility" is the level of fertility reached without any form of conscious birth control. The [[Hutterites]], a small religious group in the U.S. and Canada who resemble the better-known Amish, do not practice birth control. Therefore their fertility pattern is used as a statistical model of "natural fertility" for a population that does not use any contraception. Hutterite women average 12 children each.   

"Fecundity" is the biological ability to have children, It is a function of age, health and nutrition. Fecundity begins at menarche, is low for several years and then increases quickly to a maximum in the early 20s, then declines to menopause (about age 50). "Natural fertility" is the level of fertility reached without any form of conscious birth control. The [[Hutterites]], a small religious group in the U.S. and Canada who resemble the better-known Amish, do not practice birth control. Therefore their fertility pattern is used as a statistical model of "natural fertility" for a population that does not use any contraception. Hutterite women average 12 children each.   

===Social Components of Fertility.===

===Social Components of Fertility.===

The "Three-step Analysis" was introduced by Kingsley Davis and Judith Blake in 1956 that makes analysis of the proximate determinants of the fertility process clear.   

The "Three-step Analysis" was introduced by Kingsley Davis and Judith Blake in 1956 that makes analysis of the proximate determinants of the fertility process clear.   

*Conception. Certain physical conditions may make it impossible for a woman to conceive. This is called "involuntary infecundity." If the woman has a condition making it possible, but unlikely to conceive, it is called "subfecundity." Venereal diseases, especially gonorrhea, syphilis and chlamydia are causes. Nutrition is a factor as well; women with less than 20 percent body fat may be subfecund, a factor of concern for athletes and people susceptible to anorexia. "It takes 50,000 calories to make a baby," argues demographer Ruth Frisch. There is subfecundity in the weeks following childbirth, and it can be prolonged for a year or more through breastfeeding. A furious political debate raged in the 1980s over the ethics of baby food companies marketing infant formula in developing countries. A large industry has developed to deal with subfecundity in women and men. An equally large industry has emerged to provide contraceptive devices designed to prevent conception. Their effectiveness in use varies. On average 85% married couples using no contraception will have a pregnancy in one year. The rate drops to the 20% range when using withdrawal, vaginal sponges, or spermicides. (This assumes the partners never forget to use the contraceptive.)The rate will be only 2 or 3% when using the pill or an IUD, and drops to near 0% for implants and 0% for tubal ligation (sterilization) of the woman, or a vasectomy for the man.   

*Conception. Certain physical conditions may make it impossible for a woman to conceive. This is called "involuntary infecundity." If the woman has a condition making it possible, but unlikely to conceive, it is called "subfecundity." Venereal diseases, especially gonorrhea, syphilis and chlamydia are causes. Nutrition is a factor as well; women with less than 20 percent body fat may be subfecund, a factor of concern for athletes and people susceptible to anorexia. "It takes 50,000 calories to make a baby," argues demographer Ruth Frisch. There is subfecundity in the weeks following childbirth, and it can be prolonged for a year or more through breastfeeding. A furious political debate raged in the 1980s over the ethics of baby food companies marketing infant formula in developing countries. A large industry has developed to deal with subfecundity in women and men. An equally large industry has emerged to provide contraceptive devices designed to prevent conception. Their effectiveness in use varies. On average 85% married couples using no contraception will have a pregnancy in one year. The rate drops to the 20% range when using withdrawal, vaginal sponges, or spermicides. (This assumes the partners never forget to use the contraceptive.)The rate will be only 2 or 3% when using the pill or an IUD, and drops to near 0% for implants and 0% for tubal ligation (sterilization) of the woman, or a vasectomy for the man.   

*Gestation. After a fetus is conceived, it may or may not survive to birth. "Involunatry fetal mortality" involves miscarriages and stillbirth (a stillbirth is a fetus born dead). Voluntary fetal mortality is called "abortion," and is the single most-used form of birth control around the world. In the USA, the number of abortions has been steady at about 1.6 million a year.   

*Gestation. After a fetus is conceived, it may or may not survive to birth. "Involunatry fetal mortality" involves miscarriages and stillbirth (a stillbirth is a fetus born dead). Voluntary fetal mortality is called "abortion," and is the single most-used form of birth control around the world. In the USA, the number of abortions has been steady at about 1.6 million a year.   

==Explanations for Fertility Transition==

==Explanations for Fertility Transition==

"The Fertility Transition" takes place when a society moves from high to low fertility. All sorts of social and economic changes take place at the same time during modernization, making it hard to sort out all the causes and effects. Policy makers who want to move a particular society from high to low fertility must have a workable theory of how to get there.   

"The Fertility Transition" takes place when a society moves from high to low fertility. All sorts of social and economic changes take place at the same time during modernization, making it hard to sort out all the causes and effects. Policy makers who want to move a particular society from high to low fertility must have a workable theory of how to get there.   

Other factors such as religion and ethnicity are sometimes important. Until the 1960s, Roman Catholics typically favored much larger families than did Protestants. Mormons still do. On the other hand, Catholics also promoted religious orders of celibate nuns, as well as a celibate all-male priesthood.   

Other factors such as religion and ethnicity are sometimes important. Until the 1960s, Roman Catholics typically favored much larger families than did Protestants. Mormons still do. On the other hand, Catholics also promoted religious orders of celibate nuns, as well as a celibate all-male priesthood.   

===Baby boom: 1940-1964===

===Baby boom: 1940-1964===

'''[[Baby boom]]''': fertility fell steadily in the USA, from 1800 to 1940. Then suddenly it started going up again, reaching a new peak in 1957. After 1960 fertility started declining rapidly. In the Baby Boom years (1940-1964) women married earlier and had their babies sooner; the number of children born to mothers after age 35 did not increase. After 1960 ideal family size fell sharply, from 3 to 2 children. Couples postponed marriage and first births, and they sharply reduced the number of third and fourth births.   

'''[[Baby boom]]''': fertility fell steadily in the USA, from 1800 to 1940. Then suddenly it started going up again, reaching a new peak in 1957. After 1960 fertility started declining rapidly. In the Baby Boom years (1940-1964) women married earlier and had their babies sooner; the number of children born to mothers after age 35 did not increase. After 1960 ideal family size fell sharply, from 3 to 2 children. Couples postponed marriage and first births, and they sharply reduced the number of third and fourth births.   

In the United States in 1995, there were 110 live births per 1,000 women ages 20-24. Four decades earlier near the peak of the Baby Boom in 1958, there were 258 live births to women in the same age range.   

In the United States in 1995, there were 110 live births per 1,000 women ages 20-24. Four decades earlier near the peak of the Baby Boom in 1958, there were 258 live births to women in the same age range.   

====Easterlin Model====

====Easterlin Model====

American Economist [[Richard Easterlin]] developed an ingenious model or theory to explain the Baby Boom. He assumes first that young couples try to achieve a standard of living equal to or better than they had when they grew up. This is called "relative status;" in other words, young men in one cohort compare themselves now to where their own fathers in a previous cohort had been. Second Easterlin assumes that when jobs are plentiful, it will be easier to marry young and have more children and still match that standard of living. But when jobs are scarce, couples who try to keep that standard of living will wait to get married and have fewer children. For Easterlin, the size of the cohort is a critical determinant of how easy it is to get a good job. A small cohort means less competition, a large cohort means more competition to worry about. The assumptions blend economics and sociology, and they seem to make sense, but notice that Easterlin did not rely on surveys or interviews asking people what really motivated them.   

American Economist [[Richard Easterlin]] developed an ingenious model or theory to explain the Baby Boom. He assumes first that young couples try to achieve a standard of living equal to or better than they had when they grew up. This is called "relative status;" in other words, young men in one cohort compare themselves now to where their own fathers in a previous cohort had been. Second Easterlin assumes that when jobs are plentiful, it will be easier to marry young and have more children and still match that standard of living. But when jobs are scarce, couples who try to keep that standard of living will wait to get married and have fewer children. For Easterlin, the size of the cohort is a critical determinant of how easy it is to get a good job. A small cohort means less competition, a large cohort means more competition to worry about. The assumptions blend economics and sociology, and they seem to make sense, but notice that Easterlin did not rely on surveys or interviews asking people what really motivated them.   

One good example of the role fertility played in religion is the Israelites' use of pagan gods such as golden calves to bring fertility to the lands and their women. In most of Mesopotamia fertile land was essential to one's well-being and survival, so most pagan gods were devoted to fertility and growth.

One good example of the role fertility played in religion is the Israelites' use of pagan gods such as golden calves to bring fertility to the lands and their women. In most of Mesopotamia fertile land was essential to one's well-being and survival, so most pagan gods were devoted to fertility and growth.

==see also==

 

==See Also==

* [[Birth Control]]

* [[Birth Control]]

* [[Demographic transition]]

* [[Demographic transition]]

* [[Baby boom]]

* [[Baby boom]]

* [[Birth Rate]]

* [[Birth Rate]]

==Bibliography==

==Bibliography==

* Barrett, Richard E., Donald J. Bogue, and Douglas L. Anderton. ''The Population of the United States'' 3rd Edition (1997) compendium of data

* Barrett, Richard E., Donald J. Bogue, and Douglas L. Anderton. ''The Population of the United States'' 3rd Edition (1997) compendium of data

* Weeks, John R. ''Population: An Introduction to Concepts and Issues'' (10th ed. 2007), standard textbook

* Weeks, John R. ''Population: An Introduction to Concepts and Issues'' (10th ed. 2007), standard textbook

    

    

====notes====

==References==

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[[Category:Reproduction]]

[[Category:Reproduction]]

[[Category:Demography]]

[[Category:Demography]]