Demographic Methods

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Demographic Methods
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Studying Individual, Family and Population
Changes From Womb to Tomb
Pr (Dying)
Pr (Conception)
Pr (Ever Marrying)
0 15 Age
60 120
15 20
Age 25
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3 Days before Ovulation Day of
Ovulation 3 Days After Ovulation
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Examples of Recent Demographic Analysis

• Teen Births Racial differences
• Fertility How babies are delivered in U.S.
• Marriage How Many Never Marry
• Longevity Recent Trends in the U.S.

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Teen Births
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Types of Birth
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Percent Never Married U.S., By Age, Sex, and
Year, 2000
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Median Age at First Marriage U.S.
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Longevity
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DEMOGRAPHIC METHODS

• Where are we headed?
• Why study demographic methods?
• Satisfies BSH requirement
• Other Really Good Reasons
• Complements many disciplines
• Many applications
• Estimating Trends and Public Policy
• Social Security, Building Schools/Roads
• Increasing availability of survival data
• Skills to enhance employment
• Think at the population level

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Acquiring Practical Skills

• Numerical analysis
• Finding relevant printed electronic data
• Presenting technical information

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Computation

• Please bring a calculator to lectures and labs
• Most complex functions are
• Raising something to a power xy or ey
• Taking a natural logarithm loge(x)
• Most of the work will be handled in Excel
  spreadsheets or SAS/Stata

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Next Time

• Read Hinde Chapters 1-3
• Turn in Chapter 2 Excel problems with graphs
• http//www.prb.org/
• Look for Population A Lively Introduction on
  right panel
• Review pps 1- 22

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Demography Certificate

• Commercial Interruption

http//www.demography.utah.edu
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WHAT IS DEMOGRAPHY?

• Demography is the study of population structure
  and change Hinde, 1998
• Demography is the scientific study of human
  populations, primarily with respect to their
  size, their structure and their development
  IUSSP, 1982

Population Studies
Formal Demography
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What Makes an Analysis Demographic?(1 of 2)

• Vital Rates
• Natality, Nuptiality, Mortality, Migration
• Health, Marriage, Employment
• Linkage of Vital Rates to Population Structure
• What if everyone stopped having children or lived
  to be 200 years old? (film Children of Men)
• Demographic Theories
• Easterlin Hypothesis size of cohort affects
  individual behavior

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What Makes an Analysis Demographic?(2 of 2)

• Key Methodological Innovations
• Life Table
• Standardization and Decomposition
• Differences in vital rates (births, deaths,
  migration between two populations is due in part
  to age composition (whos older/younger) and the
  rates at each age.
• Survival Analysis
• Classic vs the New

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How Many People Have Ever Lived on Earth?

• 75 percent of the people who had ever been born
  were alive in 1970
• What do you need to know to see if this is
  reasonable???

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RATES

• Number of deaths in 2000 (these are thetas ? in
  Hinde)
• Bostwana 29,100
• Sweden 49,339
• Russia 2,051,000
• Utah 13,042 (2002)
• Population sizes in mid-2000
• Bostwana 1,651,000
• Sweden 5,176,000
• Russia 145,491,000
• Utah 2,338,761 (2002)
• M-type mortality rates
• Bostwana 29,100 / 1,651,000 0.0176
• Sweden 49,339 / 5,176,000 0.0095
• Russia 2,051,000 / 145,491,000 0.0141
• Utah 13,042 / 2,338,761 0.0056

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Death Rates

• Will return to Q-type (cohort) death rates when
  we discuss survival models
• Assume m-type death rates
• Crude death rates
• Age-specific death rates

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Using Excel and Hindes Data
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Calculating Death Rates In Excel
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PERIODS AND COHORTS

• Periods
• Time point or interval
• Period perspective looks at populations or
  subpopulations for a given year or for a series
  of years
• e.g. deaths to aged 90 in the US for 1900, 1910,
  etc.
• Cohort
• a group of people sharing a common characteristic
  followed over time
• e.g. the birth cohort of 1983, the 2001 marriage
  cohort
• Cohort perspective follows a cohort over time as
  they age

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Todays Topics

• Components of population change
• Periods and cohorts
• Ratios and proportions
• Rates and probabilities
• Lexis Diagrams
• Demographic Data

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What is a population?

• Collection of people alive at a certain point in
  time in a specified country/area who meet certain
  criteria
• Population of Salt Lake City in mid-2001 aged 65
  
• Not geographically bound
• Jewish diaspora, Mormon Pioneers
• Distinction between De jure vs. De facto
  population
• What is usual residence? Not easy to define for
  some groups, e.g. students, traveling
  communities, seasonal workers, children who
  divide time between divorced parents
• Pedigrees

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COMPONENTS OF POPULATION CHANGE

• Three components
• Births
• Deaths
• Migration
• Population change occurs because people make
  transitions between states

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E(t)
Alive and in the population
Alive and in another population
I(t)
E(t)
D(t)
Unborn
Dead
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Alive
Dead
Sterile
Sterile
Sterile
Having Had No Children
Having Had 1 Children
Having Had 2 Children
Dead
Dead
Dead
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The demographic accounting equation

• Final pop
• Initial pop births deaths immigration -
  emigration
• P(tn) P(t) B(t) D(t) I(t) E(t)
• Natural change B D
• Net balance of migration I E
• Example
• Mid-1998 pop of UK 59,237,000
• Births mid-1998 to mid-1999 711,000
• Deaths mid-1998 to mid-1999 635,000
• Net balance of international migration 188,000
• Mid-1999 pop of UK 59,501,000

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(Survey in 1985)
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RATIOS

• Ratios
• Ratio is a number divided by any other number
• e.g. x/y
• e.g. sex ratio (no. of males / no. of females)
  k
• For the UK in mid-1998 sex ratio
• (29,128,400 / 30,108,100) 100 96.7
• For 2000 Utah------?

Age Total Males Females
Other ratios include 1 The dependency ratio 2
The child-woman ratio 3 Parity progression ratios
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Proportions/Percentage

• Ratio in which the denominator includes numerator
  ? x/(x y)
• Proportion to refer to groups (rather than
  events)
• Proportion of British population from an ethnic
  minority in mid-2000 was 4,039,000 / 57,057,000
  7.1

Percentage of Hispanics by Selected Utah
Counties 2000
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Rates and Exposure

• Rate ( of events) / ( of person-years lived)
  k
• k is often 1000
• Number of person-years lived population at risk
• How are person-years defined?
• 3 people in a pop for 1 year
• Person-years 3 people 1 year 3
  person-years
• 3 people in pop for 1 year 1 person in pop for
  ½ year
• Person-years (3 people 1 yr) ( 1 person
  ½ yr)
• 3½ person-years
• Normally use mid-point pop (mean of start
  end-of-interval populations)

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Lexis Diagrams, Cohorts, and Social and
Individual Change
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maPm
q (2m)/(2m)
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Which Population has the best life expectancy???
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Trends in Life Expectancy, by Region.Life
Expectancy at Birth, in Years
Source United Nations, World Population
Prospects The 2002 Revision (medium scenario),
2003.
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Jeanne Louise Calment Died 1997 at age
122 Longest-lived person with authenticated
records Bore one child
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Sources of Data

• Vital Records
• U.S. Census Records
• Genealogies

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31 American Community Survey Test Sites

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Survey Sampling

• Sampling frames and generalizability
• Nonresponse
• Total Item
• Prospective/longitudinal
• Retrospective/cross sectional
• World Fertility Surveys - often with illiterate
  respondents
• Demographic and Health Surveys
• Self vs proxy
• Identifiers to link to other data
• Mode of administration (phone, in-person, mail,
  web)
• Questionnaire construction
• Length of survey
• Types of questions
• Factual or subjective