# Contract — F1-conf-02

Question: change in life expectancy at birth (WDI SP.DYN.LE00.IN) 2000→2022 across a fixed country set. Estimands: balanced-panel means — for each year, unweighted mean over countries (iso3) with a recorded value in every year 2000–2022, each counted once; mean_2000_balanced, mean_2022_balanced, their difference; composition of the balanced set. Meaningful as a descriptive, unweighted (not population-weighted) mean of a fixed set; not representative of the world. Baseline: mean_2022_all_available = mean over all distinct iso3 with recorded 2022 value, each once. Outputs: out/results.json (task_id, n_countries_total, n_countries_balanced, n_countries_incomplete, balanced_countries, n_analysed, mean_2000_balanced, mean_2022_balanced, change_2000_2022_balanced, mean_2022_all_available, feasibility, feasibility_reason, data_issues, n_input_rows, random_seed), out/analytic.csv, out/exclusions.csv, out/report.md (6 sections), out/analysis.py, out/claims.json. Information rules: only data/life_expectancy_panel.csv; no imputation/interpolation/lookups; empty cell = missing; country = iso3; ≤1 obs per country-year. Invalidity conditions: conflicting duplicate values for same (iso3, year) that cannot be resolved without outside info; no country complete across all years (infeasible).