Intro to Demographic Methods

🪵Intro to Demographic Methods Unit 2 – Data Sources: Census, Vital Stats, Surveys

Demography studies human populations, focusing on their characteristics, dynamics, and structure. Key concepts include population composition, cohorts, and rates that measure demographic events. Understanding these fundamentals is crucial for analyzing population trends and their societal impacts. Demographic data comes from various sources, each with unique strengths and limitations. Censuses provide comprehensive snapshots, vital statistics record life events, and surveys offer detailed insights. These sources, along with emerging big data, form the backbone of demographic research and policy-making.

Key Concepts and Definitions

  • Demography studies the characteristics, dynamics, and structure of human populations
  • Population composition refers to the distribution of various attributes within a population (age, sex, race, marital status)
  • Population dynamics encompass the processes that change population size and composition over time (fertility, mortality, migration)
  • Cohort is a group of individuals who experience the same event within the same time period (birth cohort, marriage cohort)
  • Period refers to a specific point in time or a defined time interval for which data is collected and analyzed
  • Rates measure the frequency of demographic events relative to the population at risk (crude birth rate, age-specific mortality rate)
    • Calculated as the number of events divided by the population at risk, often expressed per 1,000 or 100,000 people
  • Population pyramid graphically represents the age-sex structure of a population

Types of Demographic Data Sources

  • Census data provides comprehensive information on population size, composition, and distribution at a specific point in time
  • Vital statistics record vital events such as births, deaths, marriages, and divorces
  • Sample surveys collect detailed information from a representative subset of the population
  • Administrative records include data collected by government agencies for various purposes (tax records, social security data)
  • Population registers continuously update individual-level information on vital events and migration
  • Ethnographic data provides qualitative insights into population dynamics and cultural contexts
  • Big data sources (social media, mobile phone records) offer new opportunities for demographic analysis

Census: Purpose and Methodology

  • A census aims to enumerate and collect information on an entire population at a specific point in time
  • Provides a snapshot of population size, composition, and distribution
  • Typically conducted every 5 or 10 years, depending on the country
  • Census questionnaires collect data on demographic, social, and economic characteristics
    • Core questions cover age, sex, marital status, household composition, and housing characteristics
    • Additional topics may include education, employment, income, and migration history
  • Census data is collected through self-enumeration (households complete questionnaires) or interviews by trained enumerators
  • Data processing involves coding, editing, and imputation to ensure data quality and consistency
  • Census results are disseminated through published reports, online databases, and microdata files

Vital Statistics: Recording Life Events

  • Vital statistics systems continuously record the occurrence and characteristics of vital events
  • Vital events include births, deaths, marriages, divorces, and fetal deaths
  • Legal requirements mandate the registration of vital events with civil registration authorities
  • Birth records provide information on the newborn (sex, weight, gestational age) and parents (age, education, occupation)
  • Death records include data on the deceased (age, sex, cause of death) and circumstances of death
  • Marriage and divorce records capture the formation and dissolution of legal unions
  • Vital statistics data is compiled and published by national statistical offices or health ministries
  • Provides timely information on fertility, mortality, and nuptiality patterns
  • Allows for the calculation of key demographic indicators (crude birth rate, infant mortality rate, total fertility rate)

Surveys: Sampling and Implementation

  • Sample surveys collect detailed information from a representative subset of the population
  • Probability sampling ensures that each unit in the population has a known, non-zero chance of being selected
    • Simple random sampling selects units randomly from the entire population
    • Stratified sampling divides the population into homogeneous subgroups (strata) and samples independently within each stratum
    • Cluster sampling involves selecting clusters (geographic areas, institutions) and then sampling units within selected clusters
  • Survey questionnaires are designed to capture information relevant to the research objectives
  • Interviewer-administered surveys (face-to-face, telephone) allow for clarification and probing
  • Self-administered surveys (mail, online) provide respondents with more privacy and flexibility
  • Surveys can be cross-sectional (data collected at one point in time) or longitudinal (repeated measurements over time)
  • Specialized demographic surveys focus on specific topics (fertility, migration, health) or subpopulations (youth, elderly)

Data Collection Techniques

  • Face-to-face interviews involve direct interaction between the interviewer and respondent
    • Allows for clarification, probing, and observation of non-verbal cues
    • Suitable for complex questionnaires and low literacy populations
  • Telephone interviews are conducted remotely using landline or mobile phones
    • Cost-effective and efficient for reaching dispersed populations
    • Limited to short questionnaires and populations with high telephone coverage
  • Self-administered questionnaires are completed by respondents without an interviewer's assistance
    • Mail surveys send questionnaires to sampled households and rely on postal return
    • Online surveys use web-based platforms to collect data from internet users
    • Provides greater anonymity and reduces interviewer bias
  • Computer-Assisted Personal Interviewing (CAPI) uses electronic devices to administer surveys in-person
    • Allows for real-time data validation, complex skip patterns, and multimedia content
  • Computer-Assisted Telephone Interviewing (CATI) automates telephone survey administration
  • Mixed-mode surveys combine multiple data collection methods to improve response rates and representativeness

Strengths and Limitations of Each Source

  • Census data provides comprehensive coverage and detailed geographic granularity
    • Allows for analysis of small population subgroups and local-level planning
    • Limited by the decennial frequency and the risk of undercounting hard-to-reach populations
  • Vital statistics offer continuous and timely data on fertility, mortality, and nuptiality
    • Captures rare events (maternal deaths) and provides cause-of-death information
    • Data quality depends on the completeness and accuracy of event registration
  • Sample surveys enable the collection of detailed and specialized information
    • Provides flexibility in questionnaire design and allows for in-depth exploration of topics
    • Subject to sampling and non-sampling errors, and limited generalizability to the entire population
  • Administrative records leverage existing data collected for non-statistical purposes
    • Cost-effective and can provide longitudinal information on individuals
    • Data quality and completeness may vary across sources and over time
  • Big data sources offer high volume, velocity, and variety of data
    • Enables real-time monitoring and analysis of population dynamics
    • Biases in digital access and usage limit representativeness and interpretability

Real-World Applications and Case Studies

  • Census data informs electoral redistricting, infrastructure planning, and resource allocation
    • The US Census Bureau's decennial census guides the apportionment of congressional seats and the distribution of federal funds
  • Vital statistics are used to monitor public health, evaluate interventions, and inform policy
    • The Maternal Mortality Surveillance System in the US relies on death certificates and linkage with other data sources to identify and investigate maternal deaths
  • Fertility surveys, such as the Demographic and Health Surveys (DHS), provide insights into reproductive health and family planning
    • DHS data has been used to assess the impact of contraceptive prevalence on fertility rates in sub-Saharan Africa
  • Labor force surveys, like the Current Population Survey (CPS) in the US, monitor employment, unemployment, and labor market dynamics
    • CPS data is used to calculate the official unemployment rate and track disparities by age, sex, and race/ethnicity
  • The WorldPop project combines census, survey, and geospatial data to produce high-resolution population distribution maps
    • These maps support disaster response, disease surveillance, and resource targeting in low- and middle-income countries
  • Mobile phone call detail records have been used to estimate population displacement and migration flows
    • Analysis of mobile phone data provided insights into the spatial distribution of population movements following the 2010 Haiti earthquake


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.