Empirical Research Roadmap Template (Regression Analysis)

flowchart TB
    subgraph E1[Theory and hypotheses]
        direction LR
        A[Background and question] --> B[Literature review] --> C[Theoretical analysis and hypotheses]
    end
    subgraph E2[Research design]
        direction LR
        D[Sample and data sources] --> E[Variable definitions] --> F[Model specification]
    end
    subgraph E3[Empirical tests]
        direction LR
        G[Descriptive statistics and correlations] --> H[Baseline regression]
        H --> I[Robustness checks]
        H --> J[Heterogeneity and mechanisms]
    end
    subgraph E4[Conclusions]
        direction LR
        K[Findings] --> L[Policy implications] --> M[Limitations and outlook]
    end
    E1 --> E2 --> E3 --> E4

Draw an empirical research roadmap in Mermaid flowchart TB syntax for the topic [the effect of X on Y]. Use four subgraph phases: Theory and hypotheses, Research design, Empirical tests, Conclusions, with direction LR inside each. Steps: [background and question → literature review → theoretical analysis and hypotheses; sample and data sources (name the sample) → variable definitions → model specification (name the model); descriptive statistics → baseline regression, then two branches: robustness checks, and heterogeneity and mechanisms; findings → policy implications → limitations and outlook]. Connect the phases by their subgraph ids. Output only the mermaid code block.