Chapter 4: Demography

1. Chapter 4: Demography • aka Population Studies or Population Science • The study of human populations • Size • Composition • Distribution • Causes and consequences of changes in those characteristics

2. Demography is interdisciplinary • Many factors impact population • Demographers can be trained in • Sociology • Economics • Biology • Geography • History • Health sciences • ANTHROPOLOGY

3. Population measures • Fertility • Mortality • Migration

4. Fertility • Number of births that occur to an individual or in a population • Worldwide fertility ranges from 1.3 in Spain to 7.4 in Niger • US fertility is approx. 2.1 • Hutterite fertility was 12

5. Fecundity • Physiological ability to have children • Fecundity ranges from 0-30 in females to 0-infinity in males • Factors which limit reproduction • Cultural • Social • Economic • Epidemiological

6. Intermediate variables affecting fertility • Davis and Blake 1956 Fecundity • Ability to have intercourse, conceive, and carry to term • Sexual unions • Formation and dissolution, age at first intercourse, proportion of women in unions, time spent outside a union, coital frequency, celibacy, temporary separations • Birth control • Contraceptive use, sterilization, abortion

7. Industrialized countries • Contraceptive use and abortion most important factors

8. Developing countries • Infecundity due to STD’s, HIV/AIDS, lactational amenoreah (Interbirth interval), and postpartum abstinence (postpartum taboo) most important factors

9. Fertility patterns • This implies that people in industrialized countries want to limit their fertility and people in developing countries are limited by exogenous factors

10. Measures of fertility • Period rates • Cohort rates

11. Period rates • Total fertility rate (TFR) • Average number of children born per women in a population • Replacement level fertility • Fertility required to keep a population at its current level • Crude birth rate (CBR) • Number of births per 1000 population • General fertility rate (GFR) • Number of births per woman • Net reproductive rate (R0) • Current births plus expected births (RV)

12. Period rates cont’d. • Most of these measures focus on women 15-49 years old. Why?

13. Cohort rates • Completed fertility rate (CFR) or completed family size (CFS) • Number of live births to a woman who has completed reproduction (menopause)

14. Variation in fertility • Within a society or political entity • Between a society or political entity • Between men and women in the same society

15. Mortality: Death • Usually measured as • Crude death rate: number of deaths per 1,000 population • Worldwide range from 2 in the Persian Gulf states to 30 in civil war torn Sierra Leone • n US about 9 per 1,000

16. Death rate • Highly influence by age-structure of the population. • Where a higher percentage of the population is older, death rates tend to be higher • What about the effect of HIV/AIDS in relation to the age-specific death rate?

17. Life Expectancy • Number of years members of an age class can expect to live based on the current death rates of older age classes • Often misused, is a period rate like TFR also constructed from a life table (sum of age-specific death rates) • Not to be confused with life span • The maximum human life span now seems to be in the 120’s. Few people, however, live to be 100

18. Variation in mortality • Age • Sex • Socioeconomic status

19. Migration • Movement of people into or out of a specific geographic area • Most variable of the agents of demographic change • Difficult to measure due to lack of reporting and monitoring

20. Types of migration • In-migration (immigration) • Out-migration (emigration) • International vs. internal

21. Net migration • Difference between in- and out-migration

22. Variation in migration • Age • Young adults, life cycle changes • Gender • In Africa males migrate, in much of Asia and Latin America females migrate • Education • Extremes—both very poor and very wealthy migrate • Socioeconomic status • Depends on the type of job

23. International migrants • Major destinations for immigrants • US, Australia, Canada, European Community, Israel • Often motivated by economic hardship, war, political instability • Chain migration • Choice of destination determined by presence of social or kin network

24. Variation in international migration • Age • Young adults • Gender • Same as for internal migration • Education • Educated, often professionals • Socioeconomic status • Higher than those who stay behind

25. Population size and growth • Rate of natural increase • Crude birth rate minus crude death rate • In USA (1997) this was 14.6-8.6=6.0 (0.6%) • Worldwide this was 23.1-9.0=14.0 (1.4%) • Growth rate • Rate of natural increase+net migration • A growth rate of 1% means a population will double in 70 years

26. At present growth rates • World’s population will double in 50 years • If the growth rate doubles to 2.8%, the world’s population will double in 25 years • Conversely if the growth rate decreases by half to 0.7%, the doubling would occur in 100 years

27. Demographic balancing equation • Shows the roles of fertility, mortality, and migration in population change • Population =Births–deaths +immigrants-emigrants • Used in population projection

28. Population projection • Demographers can project population based on current rates of fertility, mortality, and migration • Also can use estimated future rates • Projections lose accuracy quickly as the projected time increases since it is difficult to know how demographic characters will be affected by variables in the future • US hit 300,000,000 on Tuesday at ~7:30am

29. Population composition • The aggregation of individual demographic characteristics on a population level • Population pyramids • Age sex composition • Four shapes: • Pyramidal—high growth • Rectangular—slow growth • Oval—decline • Hourglass—AIDS driven decline • US Census International Population Pyramid Projections

30. Other components • Sex • Race • Ethnicity

31. Race • Race as a classification has come under great fire • There may be a genetic or biological component to race, but in general it is a subjective classification which varies greatly depending on time and place. • For instance, slaves in the US could have only one-sixteenth African ancestry • Today in the US this subjective classification continues

32. Race may be useful • It gives us some idea of who might be subject to discrimination • Ethnicity refers to linguistic and/or cultural heritage and should not be confused with race

33. Population distribution • Worldwide population distribution is shifting to developing countries due to higher fertility • Both in the USA and worldwide, urbanization is a critical influence on population distribution

34. How many people can the earth support? • Carrying capacity of the earth—around 10 billion (Cohen 1995) • When will the earth reach 10 billion at current rates of growth? • Around 2035

35. Demographic Transitions • Three types of demographic transitions • Fertility • Mortality • Health (also called Epidemiologic)

36. Why are demographic transitions important? • The combined effect of demographic transitions results in very low population growth • The age structure of the population becomes older • This has effects on economy, health institutions, educational institutions

37. Geopolitics • Most international population policy oriented towards slowing population growth has focused on inducing fertility transition • This would lower fertility and slow population growth to some extent • Reversing mortality and health transitions is not ethically or politically viable

38. Theories of fertility transitions • Classical demographic theory • Economic models • Social models • Evolutionary models

39. Classical transition theory • Industrialization and modernization led to initial higher fertility due to improved health care and higher quality and more reliable food supply • Because pre-industrial societies had high mortality, higher fertility was necessary for those societies to survive • Fertility could only be expected to fall due to the effects of industrialization: higher survival, individualism, consumerism, mobile urban populations, lessening of familial ties, and decline of fatalism

40. Classical transition theory cont’d. • Three phases of fertility decline • Inicipient decline--widespread fertility control, heavy industrialization • Transitional growth--low mortality but high fertility, industrializing • High growth potential—high mortality and high fertility, very low industrialization

41. Economic explanations • Applied principles of microeconomics to children—another normal good • Differ in whether desire for children is established early in life or is based on current conditions • Supply and demand: Children are more in demand where they are less expensive • Economic value of children depends on context of subsistence economy.

42. Social explanations • Post-modernist interpretation • Ideational change is major motivator of fertility transitions • Uses diffusion theory • Ideas about the number of children to have follow linguistic boundaries and diffuse from elites and centers of power to the hinterlands

43. Evolutionary perspectives • Humans like other organisms evolved in the context of fitness maximization • Maximizing genetic representation in succeeding generations • Human lifestyles vary widely and may show great divergence from the lifestyle in which human reproductive psychology evolved • We can still understand reproductive behavior in the present as the manifestation of evolved psychological mechanisms

44. These perspectives differ in two related aspects • Theory of motivation • Are people motivated by the uptake of culturally specific roles or by their self-interest? • Acquisition and utilization of information • Do people pattern their fertility after some cultural norm or is fertility a response to environmental/economic conditions?

45. Cost/value of children • Biologists (Trivers), demographers (Caldwell), and economists (Becker) have all independently recognized that offsprings’ ability to provision themselves are important factors in determining parental fertility

46. Agriculture • Cultivation and herd animals • “Domestication” • Occurred worldwide about 12,000 years ago • Mesopotamia • Levant • China • Indus valley • Mesoamerica

49. Effects of agriculture • Agriculture changes time allocation in relation to subsistence pattern • Affects all age-sex groups • Leads to effects of sedentization • Changes diet composition • Increase in simple carbohydrates such as starch and sugar • Increased use of animal fat • Use of dairy products • Potential serious consequences in micronutrient balance

50. Epidemiological transition • Increasing health issues related to agriculture and sedentism • Diet led to vitamin/mineral deficiency in some places due to heavy reliance on one staple grain