Reading: Demographics - Slides

Demographics

Henry Reyenga

History of Demographics

The study of human populations has its roots, like sociology generally, in the societal changes that accompanied both the scientific and industrial revolutions. Some early mathematicians developed primitive forms of life tables, which are tables of life expectancies, for life insurance and actuarial purposes. Censuses, another demographic tool, were instituted for primarily political purposes:

as a basis for taxation

as a basis for political representation 

Data and Methods

Demography relies on large data sets that are primarily derived from censuses and registration statistics (i.e., birth, death, marriage registrations). Large data sets over long periods of time (e.g., the U.S. census is conducted every 10 years) are required to develop trends in demographic indicators, like birth and death rates.

In many countries, particularly in developing nations, reliable demographic data are still difficult to obtain. In some locales this may be due to the association of census with taxation.

Demographic Indicators

Because demography is interested in changes in human populations, demographers focus on specific indicators of change. Two of the most important indicators are birth and death rates, which are also referred to as fertility (see also fecundity) and mortality. Additionally, demographers are interested in migration trends or the movement of people from one location to another. 

Fertility and Fecundity

Fertility, in demography, refers to the ability of females to produce healthy offspring in abundance. Fecundity is the potential reproductive capacity of a female. Some of the more common demographic measures used in relation to fertility and/or fecundity include:

crude birth rate: the annual number of live births per thousand people

general fertility rate: the annual number of live births per 1000 women of childbearing age (often taken to be from 15 to 49 years old, but sometimes from 15 to 44).

Fertility and Fecundity

age-specific fertility rate: the annual number of live births per 1000 women in particular age groups (usually age 15-19, 20-24 etc.)

total fertility rate: the number of live births per woman completing her reproductive life if her childbearing at each age reflected current age-specific fertility rates

gross reproduction rate: the number of daughters who would be born to a woman completing her reproductive life at current age-specific fertility rates

net reproduction rate: the number of daughters who would be born to a woman according to current age-specific fertility and mortality rates

Replacement Level

Another important demographic concept relating to fertility is replacement level. Replacement level fertility refers to the number of children that a woman (or monogamous couple) must have in order to replace the existing population. Sub-replacement fertility is a fertility rate that is not high enough to replace an existing population. Replacement level fertility is generally set at 2.1 children in a woman's lifetime (this number varies by geographic region given different mortality rates). Sub-replacement fertility is below approximately 2.1 children in a woman's life time. The reason the number is set to 2.1 children per woman is because two children are needed to replace the parents and an additional one-tenth of a child is needed to make up for the mortality of children and women who do not reach the end of their reproductive years.

Woman’s Education Level

One of the strongest predictors of fertility rates is women's educational attainment. Almost universally, higher levels of educational attainment result in lower fertility rates. It is not, however, education itself that causes declines in fertility but rather its association with other factors that reduce fertility: women with higher levels of education delay marriage and are more likely to abstain from marriage and / or parenthood, have improved labor market opportunities, are more likely to use contraception during intercourse, and are less likely to adopt traditional childbearing roles

Country’s Level of Development

Fertility rates are also closely related to a country's level of development, which influences other factors.[4] For instance, women who have kids in developed countries have increased opportunity costs, meaning they will make less money because of time spent outside the workforce raising kids. This is true in developed countries because women are more likely to be highly skilled and well-paid (relative to women in developing countries). 

Country’s Level of Development

Additionally, delayed childbearing, probability of a child reaching adulthood, norms about ideal family sizes, and pervasiveness of contraceptives will all reduce fertility rates. But one of the biggest factors is the cost of children. In undeveloped and developing countries, children are often an economic asset to parents as they serve as cheap labor on the farm; they don't require pay, just food and shelter. That is not the case in developed countries, where very few people work in agriculture (roughly 2% in the US). Instead, children are an economic liability, meaning they cost money while not generating money for the parents.

Mortality

Mortality refers to the finite nature of humanity: people die. Mortality in demography is interested in the number of deaths in a given time or place or the proportion of deaths in relation to a population. Some of the more common demographic measures of mortality include:

crude death rate: the annual number of deaths per 1000 people

infant mortality rate: the annual number of deaths of children less than 1 year old per thousand live births

life expectancy: the number of years which an individual at a given age can expect to live at present mortality rates

Long Life

According to recent research,[6] one of the best predictors of longevity (i.e., a long life) is education, even when other factors are controlled: the more educated you are, the longer you can expect to live. A few additional years of schooling can add several additional years to your life and vastly improve your health in old age. The mechanism through which this works is not the schooling itself, but schooling's influence on other health-related behaviors. The more education someone has, the lower his/her likelihood of smoking and engaging in unhealthy and high risk behaviors. Education also increases the probability of people engaging in healthy behaviors, like frequently exercising

Factors for Long Life

Other factors associated with greater longevity include:

wealth: money increases access to good healthcare, which improves health and increases longevity

race: whites live longer than blacks, though this is due to other social disparities, like income and education, and not to race itself

ability to delay gratification: with the ability to delay gratification people live healthier lives and engage in healthier behaviors (e.g., exercise)

larger social networks: having a large group of friends and close relationships with relatives increases your social support, which positively influences health

job satisfaction: people in more powerful and more satisfying jobs tend to be healthier than people in less satisfying jobs

Urbanization

Urbanization is the physical growth of urban areas as a result of global change. Urbanization is also defined by the United Nations as movement of people from rural to urban areas with population growth equating to urban migration. The United Nations projected that half of the world's population would live in urban areas at the end of 2008.[20] Urbanization is closely linked to modernization, industrialization, and the sociological process of rationalization