Demographic Surveys: Collecting and Analyzing Population Data
Asking Questions About Populations
Demographic surveys are a primary tool for collecting information about populations. While censuses attempt to count everyone, surveys collect detailed information from samples of the population. Surveys can explore topics that censuses cannot—fertility intentions, migration histories, health behaviors, and attitudes.
Well-designed surveys provide accurate information about populations at a fraction of the cost of censuses. They are essential for demographic research, policy analysis, and program evaluation.
Survey Design
Questionnaire Design
Good questions are clear, specific, and unbiased. Question wording and order affect responses. Cognitive testing helps identify problems.
Sampling
Probability sampling ensures that every member of the population has a known chance of selection, enabling statistical inference.
Data Collection
Surveys are conducted through face-to-face interviews, telephone, mail, or online. Each mode has strengths and limitations.
Major Demographic Surveys
Demographic and Health Surveys
The DHS program has conducted standardized surveys in over ninety countries since 1984.
Other Survey Programs
The World Fertility Survey, the Multiple Indicator Cluster Surveys, and national surveys such as the Current Population Survey and the American Community Survey are essential data sources.
Survey Analysis
Descriptive Statistics
Surveys provide estimates of population characteristics such as fertility rates, contraceptive use, and child mortality.
Multivariate Analysis
Regression and other methods examine relationships among variables while controlling for confounding factors.
Sampling Weights
Surveys typically require weighting to adjust for unequal selection probabilities and non-response.
Challenges
Non-Response
Declining response rates are a major challenge. Non-response can bias survey estimates.
Measurement Error
Respondents may misunderstand questions, forget information, or give socially desirable answers.
Cost
High-quality surveys are expensive, especially face-to-face surveys in difficult settings.
FAQ
What is the difference between a census and a survey?
A census attempts to count every person in the population. A survey collects data from a sample. Surveys are less expensive and can collect more detailed information.
How large must a survey sample be?
Required sample size depends on the precision needed, the variability of the characteristic being measured, and the design effect. Larger samples are needed for rare characteristics or small subgroups.
What is sampling error?
Sampling error is the difference between a survey estimate and the true population value due to random sampling. It can be quantified through confidence intervals and margins of error.
How are surveys adapting to declining response rates?
Strategies include mixed-mode designs, incentives, improved training, and the use of administrative data to supplement surveys.
Conclusion
Demographic surveys are essential tools for understanding population dynamics. Good survey design and analysis produce information that is critical for research, policy, and programs. For further reading, see census data analysis and the study of population measurement.