# Contract (P0)

Question. 12-month growth of CPIAUCSL (SA) for each month 2001-01..2026-09: g_t = 100*(P_t/P_{t-12}-1), P from the most recent vintage covering month (2026-10-28 vintage for 2014-01..2026-09, else 2016-07-15 vintage). Estimands. g_t per month; mean over window (over months where g_t computable); sub-period means 2001-01..2013-12 (baseline) and 2014-01..2026-09; g for 2014-06, 2016-07, 2020-05, 2022-06, 2026-09; max/min and their months; counts of computable/missing months. Meaningful assuming the vintage values are faithful copies of ALFRED; note that g_t near 2014-01..2014-12 mixes vintages (P_t from 2026 vintage, P_{t-12} from 2016 vintage) as dictated by the rule. Outputs. out/results.json (keys per TASK.md table), out/analytic.csv (date,cpi,cpi_lag12,vintage_used,growth_12m; n_analysed rows), out/exclusions.csv, out/report.md (6 sections), out/analysis.py, out/claims.json. Information rules. Latest vintage wins; no interpolation/imputation; missing g_t reported and counted; only data/ files. Assembled file is non-authoritative. Invalidity. Using assembled file values where they conflict with vintages; imputing missing levels; using an older vintage where newer exists.