Drift

All drift credible intervals included zero. Estimated drift values fell below detectability thresholds, so any true directional trend would be smaller than the data can reliably separate from stochastic variation. Posterior directional indices provided weak evidence for sustained change. Sensitivity analyses starting at ages 50, 60, and 70 found no sustained drift in the Gompertz slope. Even the strongest directional indications in France did not meet the paper's evidence standard for sustained drift.