Last Time

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Last Time

• Introduction
• Some recent demographic trends
• Notation
• Age-period-cohort

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Today

• Demographic rates
• M vs q (period vs cohort)
• Lexis diagrams
• Comments on data sources
• Confounding and standardization
• Errata sheet

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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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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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Bare Branches
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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 and Cohorts
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maPm
q (2m)/(2m)
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Sources of Data

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

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31 American Community Survey Test Sites

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Surveys (1of 2)

• Sampling
• Sampling frames and generalizability
• Coverage - RDD
• Nonresponse -Total Item
• Prospective/longitudinal
• Retrospective/cross sectional
• World Fertility Surveys - often with illiterate
  respondents
• Demographic and Health Surveys

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Surveys (2 of 2)

• Who and How You Get It
• Self vs Proxy
• Identifiers to link to other data (SSN)
• National Death Index
• Mode of administration
• Questionnaire construction
• Length of survey
• Types of questions
• Factual or subjective

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Comparing Populations

• Whats the Problem?
• Apples and Oranges
• Why Bother?
• If the differences are real, helps to identify
  population and public health trends and problems

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Confounded

• Two populations have different crude death rates
  (m). Why are they different?
• Need to rule out the obvious age since it has
  a profound effect on mortality, fertility and
  migration
• Even after ruling out age, can still be other
  things to rule out as well sex, race, etc.
• Start with age and then standardize population
  structures with respect to age

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Dealing with Age Confounding

• Direct standardization
• Age Standardized Death Rates (ASDR)
• Indirect standardization
• Standardized Mortality Ratio (SMR)

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Age Standardization

• Eliminate age-distribution differences
• Amx Pop A m-type death rate for age group x
• SPx Population exposed to risk of death in some
  standard population for age group x
• ASDR for Pop A

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What is the ASDR?

• What does this do?
• The expected deaths for population A if you
  assume you have the age-specific death rates of
  population A but the age-structure of a standard
  population

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What is the ASDR?

• Another way to state this
• ASDR is
• Crude Death Rate of Standard Population times the
  Comparative Mortality Factor

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Another Perspective The CMF
Exp Deaths in Std Pop if it had Pop A
Age-specific DR Actual Deaths in Std Population
(Crude Death Rate in the Standard Population)
ASDR
x
This is the Comparative Mortality Factor (CMF) or
Ratio of Death Rates Between Pop A and Std Pop
Deaths at age x in Std Pop
Total Deaths in Std Pop