{
  "name": "back-cast, life expectancy: the UN's Bayesian hierarchical model, alone and stacked with the pooled-gain model",
  "registered": "2026-10-04",
  "target": "docs/LIVES.md target 2 as revised: MAE in 2019 at most 1.2 years in countries without HIV epidemics or major wars, at most 1.8 overall",
  "data": {
    "source": "UN World Population Prospects 2024, WPP2024_Demographic_Indicators_Medium.csv.gz: LExFemale and LExMale, annual, the same 155 countries as backcast-e0.json (LocTypeID 4, 1M+ people in 2000)",
    "caveat": "as backcast-e0.json: WPP 2024 re-estimates the past with later censuses; every method sees the same revised past"
  },
  "shock_countries": {
    "rule": "decided from data up to 1999 only, so the split is not chosen by the outcome: a country is a shock country if its female life expectancy fell by 3 years or more over any 5 consecutive years in 1980-1999 (an epidemic or a war shows as a fall), or if it was named a generalised HIV epidemic country in Raftery et al. 2013 (the 38 their validation excluded)",
    "report": "the list of shock countries is written before any forecast is scored"
  },
  "methods": {
    "bayes": "bayesLife 5.3.1 (CRAN): run.e0.mcmc annual, female, 3 chains of 20,000 iterations, thinned, burn-in half; male by the joint female-and-gap model (e0.predict with joint.male); fitted on the series up to the cut-off year only (my.e0.file holding nothing after it); the forecast is the posterior median",
    "pooled": "e0.ts with robust: true (the frozen crisis-robust pooled-gain model of backcast-e0-robust.json)",
    "stack": "w * bayes + (1 - w) * pooled, per sex, with w in 0..1 chosen to minimise MAE on the nested holdout (both fitted up to 1979, scored on 1999), then fixed and applied to the forecasts fitted up to 1999"
  },
  "outcomes": {
    "primary": "MAE in 2019 by sex, overall and in the countries that are not shock countries, for bayes, pooled and stack",
    "also": "the irreducible share: overall MAE minus non-shock MAE per method; bayes 80% interval coverage; the 10 worst countries",
    "decision": "the revised target is met if the stack's (or bayes's) non-shock MAE is at most 1.2 AND its overall MAE at most 1.8, for both sexes. All methods are reported whatever happens."
  },
  "seed": 20261004
}