popdevr-research-design

Research Design (popdevr-research-design)

PDR accepts a wide range of approaches — empirical demography, formal demography, and conceptual synthesis — but is demanding about each, and it asks one extra question: does the design illuminate the population-and-development linkage, not just a demographic quantity? The design must credibly connect the argument (popdevr-theory-building) to evidence a broad readership will trust. This skill is method-aware: pick the section that matches your question and defend it against the strongest rival.

When to trigger

• Choosing the method that actually answers a population-and-development question
• A reviewer questioned the rate construction, the identification, or the development linkage
• Specifying a decomposition, event-history, age-period-cohort, or projection design
• Justifying why your design adjudicates the rival account from popdevr-literature-positioning

Match the method to the question

• Life tables — for survival, life expectancy, and exposure: period vs. cohort, abridged vs. complete; multiple-decrement (cause-specific) where the development story is cause-specific.
• Decomposition — to attribute a difference or change in a rate to components: Kitagawa (rate vs. composition), Arriaga (age contributions to e0), Das Gupta (multi-factor). Say exactly what each component means and which maps to a development channel.
• Event-history / survival — for timing and transitions (first birth, migration, mortality), with competing risks where several destinations matter; check the proportional-hazards assumption.
• Age-period-cohort — confront the identification problem head-on: state the constraint or modeling assumption (and its justification); do not present a single "identified" APC partition as assumption-free.
• Projections / cohort-component — make transition rates, the base population, and assumptions (closed/open, period/cohort, policy scenarios) explicit; report sensitivity to key assumptions; PDR values scenario projections tied to development or policy futures.

When the question is causal (population ↔ development)

• Identification first. State the estimand and the assumptions licensing a causal reading (ignorability, parallel trends, exclusion, continuity); defend them, do not assert them.
• Selection and exposure are demographic hazards: mortality selection, migration selection, and differential exposure can masquerade as effects — address them explicitly.
• Two-way causation. Population and development often co-move; name the direction you claim and the observable that separates it from the reverse (reverse causation, institutional confounding).
• Inference. Cluster at the right level (household, region, country); use survey/design weights; report uncertainty for derived quantities.
• Sensitivity. How strong must an unobserved confounder (or a violated assumption) be to overturn it?

The adjudication test (PDR-specific)

For the single strongest rival explanation (e.g., reverse causation, compositional change, selection, institutional confounding), write one sentence: "If the rival were true rather than my account, the pattern would look like ___; instead it looks like ___." If you cannot, the design does not yet identify the population-and-development contribution.

Cross-country comparability (a recurring PDR design problem)

PDR papers often compare countries or development contexts, and a cross-national contrast is only as good as its comparability. Before reading a between-country gap as a development effect, settle three things:

1. Definitions and coverage. Are the demographic concepts (a "birth," a "migrant," an age cutoff) and the denominators measured the same way across settings? Vital-registration coverage and census quality vary with development level — and that variation can create the gradient you are studying.
2. Data class and vintage. Mixing a high-quality register with a single DHS round, or different WPP vintages, can manufacture artefactual differences. Hold the data class and vintage as constant as the question allows, and report what you could not harmonize.
3. Like-with-like comparison. Where full comparability is impossible, restrict to the subset that is comparable, or model the measurement difference explicitly rather than absorbing it into the estimate.

State which of these you have controlled and which remain a caveat in popdevr-tables-figures notes.

When the contribution is a synthetic essay (no new estimate)

If the paper's contribution is a framework rather than an analysis, the "design" is the argument architecture: the propositions, the evidence marshaled for each, and the boundary where the framework stops applying. Route the rigor through popdevr-theory-building and popdevr-writing-style instead of this skill's estimation machinery, but still pass the adjudication test against the prior framework it revises.

Anti-patterns

• Running a regression when the question calls for a life table, a decomposition, or an event-history model
• Presenting an APC decomposition without naming the identifying constraint
• Period rates read as cohort experience (or vice versa) without justification
• Ignoring mortality/migration selection or the population↔development direction of causation
• Projections whose assumptions are buried instead of varied and reported

Output format

【Method】life table / decomposition / event history / APC / projection / causal
【Quantity / estimand】what is measured or identified + its development linkage
【Key assumption(s)】and how each is defended (name the APC constraint if used)
【Rival ruled out】the adjudication sentence (incl. reverse causation if relevant)
【Robustness/sensitivity】planned checks
【Next】popdevr-data-analysis

Supplementary resources

• ../../resources/external_tools.md — life-table, decomposition, survival, APC, and projection packages
• ../../resources/official-source-map.md — PDR scope and methodological breadth