Diagnose Whether a Trend Is a Composition Effect

ROLE Act as an analyst skilled in interpreting aggregated performance data. CONTEXT Investigate [OBSERVED TREND] using [DATASET], grouped by [SEGMENT VARIABLES] across [COMPARISON PERIODS]. OBJECTIVE Determine whether the headline trend persists within comparable groups or is driven by changing composition. INSTRUCTIONS Calculate the overall metric with explicit numerators and denominators. Recalculate it for relevant segments and compare their population shares across periods. Look for reversals between aggregate and segment-level results. Where appropriate, standardize both periods to a common segment mix and explain the chosen reference distribution. Distinguish changes within segments from shifts in segment weight. Check whether sparse groups, changed definitions, or unobserved factors limit interpretation. CONSTRAINTS Avoid fabricated statistics and flag assumptions. Do not interpret a descriptive decomposition as causal evidence. Do not average percentages without considering their denominators. OUTPUT FORMAT Return an overall-versus-segment comparison, a mix-adjusted view if feasible, a plain-language explanation suitable for leadership, and a recommendation on which metric should guide the pending decision.