Fertility factors are determinants of the number of children that an individual is likely to have. Fertility factors are mostly positive or negative correlations without certain causations.
Factors associated with increased fertility include the intention to have children, remaining religiosity, general inter-generational transmission of values, high status of marriage and cohabitation, maternal and social support, rural residence, a small subset of pro-family social programs, low IQ, personality traits such as conscientiousness, and generally increased food production.
Factors generally associated with decreased fertility include rising income, value and attitude changes, education, female labor participation, population control, age, contraception, partner reluctance to child-bearing, infertility, pollution, and obesity.
Factors associated with increased fertility Intention
The predictive power of intentions continues to be debated. Research that argues that intentions are a good predictor of actual results tends to draw ideas from the theory of planned behavior (TPB). According to the TPB, intentions stem from three factors: attitudes regarding children, including the cost of raising them versus perceived benefits; subjective norms, for example the influence of others; and perceived control over behavior, that is, how much control an individual has over their own behavior.
Fertility intentions tend to boil down to quantum intentions, or how many children to bear, and tempo intentions, meaning when to have them. Of these, quantum intention is the poor predictor because it tends to change as a result of the ups and downs of a typical life. Tempo intention is a somewhat better predictor, but still a weak way to predict actual results.
The intention to have children generally increases the probability of having children. This relation is well evidenced in advanced societies, where birth control is the default option.
A comparison of a survey to birth registers in Norway found that parents were more likely to realize their fertility intentions than childless respondents. Part of the research project Family Dynamics, Fertility Choices and Family Policy (FAMDYN) It was also suggested that childless individuals may underestimate the effort of having children. On the other hand, parents may better understand their ability to manage another child. Individuals intending to have children immediately are more likely to achieve this within two years, whereas in contrast, the fertility rate was found to be higher among those intending to have children in the long term (after four years). Stability of fertility intentions further improves the chance to realize them. Such stability is increased by the belief that having a child will improve life satisfaction and partner relationships.
Chances of realizing fertility intentions are lower in post-Soviet states than in Western European states.
There are many determinants of the intention to have children, including: The mother's preference of family size, which influences that of the children through early adulthood. Likewise, the extended family influences fertility intentions, with an increased number of nephews and nieces increasing the preferred number of children. Social pressure from kin and friends to have another child. Social support. A study from West Germany found that both men receiving no support at all and receiving support from many different people have a lower probability of intending to have another child than those with a moderate degree of support. The negative effect of support from many different people is probably related to coordination problems. Happiness, with happier people tending to want more children. A secure housing situation. Religiosity.
Fertility preference The Preference Theory suggests that a woman's attitudes towards having children are shaped early in life. Furthermore, these attitudes tend to hold across the life course, and boil down to three main types: career-oriented, family-oriented, and a combination of both work and family. Research shows that family-oriented women have the most children, and work-oriented women have the least, or none at all, although causality remains unclear.
Preferences can also apply to the sex of the children born, and can therefore influence the decisions to have more children. For instance, if a couple's preference is to have at least one boy and one girl, and the first two children born are boys, there is a significantly high likelihood that the couple will opt to have another child.
Religiosity A survey taken place in 2002 in the United States found that women who reported religion as "very important" in their everyday lives had a higher fertility than those reporting it as "somewhat important" or "not important".
For many religions, religiosity is directly associated with an increase in the intention to have children. This appears to be the main means by which religion increases fertility. Pages 238-244 For example, as of 1963, Catholic couples generally had intentions to have more children than Jewish couples, who in turn, tended to have more children than Protestant couples. Among Catholics, increased religiosity is associated with the intention to have more children, while on the other hand, increased religiousness among Protestants is associated with the intention to have fewer children.
It has also been suggested that religions generally encourage lifestyles with fertility factors that, in turn, increase fertility.Page 118 in: For example, religious views on birth control are, in many religions, more restrictive than secular views, and such religious restrictions have been associated with increased fertility.
Religion sometimes modifies the fertility effects of education and income. Catholic education at the university level and the secondary school level was associated in 1963 with higher fertility, even when accounting for the confounding effect that higher religiosity leads to a higher probability of attending a religiously affiliated school. Higher income was also associated with slightly increased fertility among Catholic couples, however, was associated with slightly decreased fertility among Protestant couples.
Parents' religiosity is positively associated with their children's fertility. Therefore, more religious parents will tend to increase fertility.
A 2020 study found that the relation between religiosity and fertility was driven by the lower aggregate fertility of secular individuals. While religiosity did not prevent low fertility levels (as some highly religious countries had low fertility rates), secularism did prevent high fertility (as no highly secular country had high fertility rates). Societal level secularism was also a better predictor of religious individuals' fertility than secular individuals, largely due to the effects of cultural values on reproduction, gender and personal autonomy.Schnabel, Landon. 2016. "Secularism and Fertility Worldwide". SocArXiv. July 19. doi:10.31235/osf.io/pvwpy.
In the book Shall the Religious Inherit the Earth?, Eric Kaufmann argues that demographic trends point to religious fundamentalists greatly increasing as a share of the population over the next century. Other scholars have argued that this may be a form of "cultural selection" that will affect future demographics due to certain religious groups having high fertility that is unexplained by other factors such as income.
Intergenerational transmission of values The transmission of values from parents to offspring (nurture) has been a core area of fertility research. The assumption is that parents transmit these family values, preferences, attitudes and religiosity to their children, all of which have long-term effects analogous to genetics. Researchers have tried to find a causal relationship between, for example, the number of parents' siblings and the number of children born by the parents own children (a quantum effect), or between the age of the first birth of the parents' generation and age of first birth of any of their own children (a tempo effect).
Most studies concerning tempo focus on teenage mothers and show that having had a young mother increases the likelihood of having a child at a young age.
In high-income countries, the number of children a person has strongly correlates with the number of children that each of those children will eventually have.
Danish data from non-identical twins growing up in the same environment compared to identical twins indicated that genetic influences in themselves largely override previously shared environmental influences. The birth order does not seem to have any effect on fertility.
Other studies, however, show that this effect can be balanced by the child's own attitudes that result from personal experiences, religiosity, education, etc. So, although the mother's preference of family size may influence that of the children through early adulthood, the child's own attitudes then take over and influence fertility decisions.
Marriage and cohabitation The effect of cohabitation on fertility varies across countries.
In the US cohabitation is generally associated with lower fertility. However, another study found that cohabiting couples in France have equal fertility as married ones. Russians have also been shown to have a higher fertility within cohabitation.
Survey data from 2003 in Romania showed that marriage equalized the total fertility rate among both highly educated and limited-education people to approximately 1.4. Among those cohabiting, on the other hand, a lower level of education increased the fertility rate to 1.7, and a higher level of education decreased it to 0.7. Another study found that Romanian women with little education have about equal fertility in marital and cohabiting partnerships.
A study of the United States, and multiple countries in Europe, found that women who continue to cohabit after giving birth have a significantly lower probability of having a second child than married women in all countries, except those in Eastern Europe.
Maternal support Data from the Generations and Gender Survey showed that women with living mothers had earlier first births, while a mother's death early in a daughter's life correlated with a higher probability of childlessness. On the other hand, the survival of fathers had no effect on either outcome. Co-residence with parents delayed first births and resulted in lower total fertility and higher probability of childlessness. This effect is even stronger for poor women.
Social support Social support from the extended family and friends can help a couple decide to have a child, or another one.
Studies mainly in ex-communist Eastern European countries have associated increased fertility with increased social capital in the form of personal relationships, goods, information, money, work capacity, influence, power, and personal help from others.
Research in the U.S. shows that the extended family willing to provide support becomes a "safety net". This is particularly important for single mothers and situations involving partnership instability.
Rural residence