Demography 101

1. Demography 101 Texas Demographic Conference Austin, Texas May 23, 2018

2. Demography the scientific study of human populations, primarily with respect to their size, their structure and their development’ (United Nations 1958). the study of human population in relation to the changes brought about by the interplay of births, deaths and migration’ (Pressat 1985).

3. Study of population size distribution composition components of population change, and determinants and consequences of population change social and economic characteristics of populaiton

4. Population Pyramids for thefour demographic transition phases

5. Texas Population Pyramid by Race/Ethnicity, 2014 Source: Texas Demographic Center, 2014 Population Estimates

6. Texas Population Pyramid by Race/Ethnicity, 2014 Source: Texas Demographic Center, 2014 Population Estimates

7. Texas Population Pyramid by Race/Ethnicity, 2014 Source: Texas Demographic Center, 2014 Population Estimates

8. Demographic Data • Three basic sources of demographic data • National censuses, registers, and surveys • National censuses • Conducted on a decennial or quinquennial basis • A “snapshot” of the population, intended to provide a picture at one point in time of the size, characteristics and distribution of a population

9. Demographic Data • Registers • Gathered continuously • Compiled and published annually or monthly • Major population events, such as births, deaths, marriages, divorces, and sometimes migration • As a birth or death occur, it is registered with the government and thus registration occurs continuously

10. Demographic Information • Censuses and registers are intended to cover the entire population • In the national census everyone is intended to be enumerated and all demographic events should be registered • Surveys are by definition administered to only a fraction of the population • Include information typically found in censuses and registers, but also include items of interest to demographers not usually included in censuses and registers

11. National Census • Decennial U.S. Census • Typically one person answers all questions pertaining to themselves and all individuals in the household • Few questions, pertaining to sex, age, Hispanic origin, household relationship, owner/renter status of residence • This is the 100% census form

15. Registration Systems Registration systems identify the population’s demographic events Registers are dynamic and continuous Principally apply to births and deaths, although some countries also register marriages, divorces, migrations and abortions

16. U.S. Birth and Death Certificates • Birth certificates include data on: • Parents, pregnancy, method of delivery, etc • Death certificates include data on: • Age, occupation, cause of death, etc • Some information death certificates come from family or others so data can be less reliable

17. Surveys Demographers also rely on a third source of data—the survey This is so because often censuses and registration systems don’t contain the extensive kinds of information needed to address some critical demographic questions Surveys are administered to carefully selected samples of the larger population

18. Popular Demographic Surveys • World Fertility Surveys—began in the 1970s, collect data on the reproductive behavior and related social and psychological indicators. Conducted in 62 countries, representing 40 percent of the world’s population • Demographic and Health Survey—More than 200 sample surveys carried out in more than 75 developing countries between 1986 and now. Areas of fertility, population, health and nutrition. Nationally representative, large sample sizes, conducted every 5 years

19. Popular Demographic Surveys • Other fertility studies—less comprehensive but also widely used: • Indianapolis Study, Princeton Study, etc • Current Population Survey (CPS)—monthly, nation-wide survey conducted by the U.S. Census Bureau. Main focus is labor-force data, provides data on unemployment in the U.S. Nationally representative sample of the U.S. population

20. Popular Demographic Surveys National Survey of Family Growth (NSFG)—conducted by the NCHS, conducted every few years since 1973. Nationally representative sample of females (males were included since 2002 version) aged 15-44, asks about sexual and reproductive health National Survey of Adolescent Health—began in 1990’s by the Carolina Population Center, covers adolescents

21. American Community Survey American Community Survey (ACS)—Redesign of the decennial census in the U.S. Replaces the long form questionnaire with a “continuous measurement” survey of the U.S. population. Started on a limited basis in 1996, in 2010 completely replaced the long form census. Data collected are be similar to the long form census.

22. American Community Survey • ACS data are estimates • ACS data are not counts of the population or housing • Population counts are produced from the decennial census • Counts are updated throughout the decade through the Population Estimates Program

23. American Community Survey (cont) ACS estimates are period estimates Period estimates describe the average characteristics over a specific time period Contrast with point-in-time estimates that describe characteristics as of a specific date

24. American Community Survey (cont) • Sampling Error • Standard Error (SE) • Margin of error (MOE) • Confidence Interval (CI) • Coefficient of Variance (CV)

25. A sample of population and housing unit records from the American Community Survey Allows users to create custom tables that are not available through pretabulated ACS products The 1-year ACS PUMS file represents 1 percent of the U.S. population What is the ACS PUMS file?

26. Definition A period estimate that encompasses more than one calendar year Period for ACS multiyear estimates is 5 calendar years (used to have 3 year) What is a Multiyear Estimate?

27. Population Thresholds for ACS Estimates

29. Measuring Population Change • Population change is simply the difference in population between two points in time. • Change can be expressed in Absolute or Percentage terms. • Absolute Change: The simple difference between population figures. Negative values indicate a loss in population. • Percent Change: The relative growth rate over a period of time calculated as a percentage using the formula: [(New-Old)/Old] *100

30. Migration Mortality Fertility Components of Population Change • Demographers rely upon the “Demographic Balancing Equation” to very simply and elegantly summarize population change: • Pop2 = Pop1 + B – D + IM – OM, where • Pop2 = Population at a later time period • Pop1 = Population at an earlier time period • B = Births • D = Deaths • IM = In-Migration • OM = Out-Migration • The nature of population change is simple… changes can only occur through: 1) Births, 2) Deaths, or 3) Migration

31. Top Counties for Numeric Growth in Texas, 2016-2017

32. Fertility Component • Fertility: The number of births that occur to an individual or in a population.  • Fecundity: The physiological ability of individuals or couples to have children. Maximum fecundity for a population is believed to be 15 children. • Another key concept is the “at-risk population”. Only a certain subset of the population is “at-risk” for fertility  Women aged 12-50 • Factors that affect fertility include: 1) Gender 4) Socioeconomic status 2) Age 5) Others Religion, Culture, Education 3) Race/Ethnicity • Common calculations related to fertility include:1) Total Fertility Rate: Average # of children in a “synthetic” family2) General Fertility Rate: #Births per 1000 women of childbearing age3) Crude Birth Rate: # Births/Midyear Population

33. Mortality Component • Mortality: Number and causes of deaths in a population. • Life Span: The upper limit to human lives is theorized to be somewhere around 120, although there are reports of some people living as long as 135 years. • Factors affecting mortality include: 1) Age (J-curve) 4) Race/Ethnicity 2) Gender 5) Modernity 3) Socioeconomic status • Common calculations related to mortality include:1) Overall Death Rate: Deaths per 1000 population2) Crude Death Rate: # Deaths/Midyear Population3) Age-Sex-Race specific survival rates: The likelihood that an individual with certain characteristics will survive the year 4) Life Expectancy: The expected number of years an individual will live if they were to live their entire life right now. In 1900~30 (worldwide) By 2000~70 (worldwide)

34. Migration Component • Migration: The movement of people into and out of a certain area. • Migration can occur at all geographic levels. 1) Neighborhood 2) Within a county 3) Across states: Out-migration versus In-migration 4) To a different country: Emigration (out of a country) versus Immigration (into a country) • Migration in the United States:Approximately 20% of Americans move per year Americans move about 11 times over their lifetimes (on average) • Factors affecting migration include 1) Age 2) Gender 3) Socioeconomic Status 4) Race and Ethnicity

35. Total Population and Components of Population Change in Texas, 1950-2010

36. Estimates of percent components of population change, Texas, 2011-2017 Source: U.S. Census Bureau, 2017 Vintage population estimates

37. Comparative measures Population at risk Average over a period Mid-year denominator, ½ numeric change numerator Rate - The ratio of the number of demographic events (e.g. births) to the population at risk of experiencing the event. In mathematical demography, the denominator is the number of person years lived. Ratio -The size of a number relative to another convenient number. Proportion - A ratio in which the denominator includes the numerator. Percentage - A proportion multiplied by 100. Probability - The ratio of the number of demographic events to the initial population at risk of experiencing them. In mathematical demography, the denominator is the number of preceding events.

38. Basic Measures of Change Crude Rates CBR = live births in a year/mid-year population * k CDR = deaths in a year/mid-year population * k RNI = (births-deaths)/mid-year population * k RNM = net migration in a year/mid-year population * k

40. Fertility • Fertility refers to the actual production of children, which is in the strictest sense a biological process • We can study fertility cross-sectionally, i.e., with period measures, or over time • On a cohort or period basis • On a micro or macro basis

41. Conceptualization and Measurement of Fertility • There are 3 main fertility concepts: • Fertility is the actual production of male and female births; fertility refers to actual behavior. • Reproduction is also actual production, but refers to the production of only female births (there is no demographic term referring to the production of only male births). • Fecundity refers to the potential or the biological possibility of producing births.

42. Conceptualization and Measurement of Fertility • The Crude Birth Rate (CBR) • A cross-sectional measure • In the world the CBR in 2007 ranged from a high of 38 in Africa to a low of 10 in Europe • It is a "crude" measure because its denominator includes people who are not at the risk of childbearing (women under 15 yrs and women over 50, and men).

43. Conceptualization and Measurement of Fertility • The General Fertility Rate (GFR) • Another cross-sectional measure of fertility. • The GFR is superior to the CBR because it restricts its denominator to women of childbearing ages. • Denominator is sometimes further restricted to women aged 15-44 because of the very low fertility among women over 44 yrs • In the U.S. more than 56 babies born in 2005 for every 1,000 women between the ages of 15 and 49

44. Conceptualization and Measurement of Fertility • The Age-specific Fertility Rate (ASFR) • Births to women according to their age. • ASFRs are usually calculated for women in each of the seven 5-year age groups of 15-19,…45-49. Sometimes 35 single year age groups are used. • ASFRs in 1970, as well as in 2000-05, are highest in Africa and lowest in Europe and North America • Table 3.1 shows the numbers of women in the U.S. in 2005 in each of the seven age groups and the numbers of babies born to the women in each of the age groups.

45. Fertility Data and Rates for the United States in 2005

46. Conceptualization and Measurement of Fertility • The Total Fertility Rate (TFR) • Like the ASFR it takes into account the fact that fertility varies by age, but the TFR provides a single fertility value • The TFR is calculated by summing the ASFRs, after multiplying each by the width of the age interval • It is a standardized rate—it is not influenced by the differences in the numbers of women in each age

47. Fertility Change in the United States Figure 3.5 shows total fertility rates for the United States from 1800 to 2007

49. Mortality • Everyone of us has been born, and everyone of us will die, but death does not occur to everyone at the same time • The length of time we will live depends on many factors; over some of these factors we have no control, but over others we have a lot of control • The impact of mortality varies significantly according to social and demographic characteristics.

50. Measurement of Mortality • An exact figure for the human life span or for the life span of any species is not known • Demographers often use the “maximum recorded age at death” as an accepted operational definition of the human life span • The longest known and verified life span, as of 2010, is 122 years and 164 days, lived by the Frenchwoman Jeanne Louise Calment. • The concept of life expectancy is used by demographers much more so than the concept of the life span.