AN-009: Aggregation within buyer-item-month cells¶
Economic intuition
Group purchases into buyer-item-month cells and ask two questions: how much was bought, and in how many separate pieces. Administrative cells move more total quantity, consistent with buying at greater scale. Litigated cells are split into more separate purchase-offer-items, consistent with demand arriving in fragmented, repeated batches. Neither fact alone settles the mechanism; together with the decomposition figure and winner switching they point toward a scale and sourcing reading.
Question¶
If the regime contrast reflects lost scale and more fragmented sourcing under litigation, that should show up when purchases are aggregated into buyer-item-month cells: administrative cells should carry larger total accepted quantity, while litigated cells should be split across more repeated purchase-offer-items.
Design¶
- Sample: common buyer-item-month cells observed under both regimes within the BEC group 65 São Paulo pharmaceutical sample, 2009–2019.
- Specification: aggregation within buyer-item-month cells, comparing total accepted quantity and the count of repeated purchase-offer-items across administrative and litigated cells.
- Role: diagnostic and suggestive. Common buyer-item-month cells are a selected subsample; the pattern supports the scale and sourcing reading only together with the decomposition figure and the winner-switching evidence.
Results¶
| Cell quantity | Administrative cells | Litigated cells |
|---|---|---|
| Total accepted quantity | Larger (greater scale) | Smaller |
| Repeated purchase-offer-items | Fewer | More (more fragmented repeated demand) |
Output: v10-causal-mechanism/output/tables/tab_aggregation_cells.tex.
Interpretation¶
Confidence: yellow. The pattern is mixed but coherent: administrative cells carry larger total accepted quantity, consistent with greater scale, while litigated cells show more repeated purchase-offer-items, consistent with more fragmented repeated demand. This is diagnostic and suggestive, not decisive. Common buyer-item-month cells are a selected subsample, so the comparison conditions on cells that appear under both regimes. The scale and sourcing reading holds only in combination with the pricing-versus-sourcing decomposition figure and the winner-switching evidence; on its own this cell-level pattern does not pin down the mechanism. The reading is yellow because the evidence is from a single jurisdiction (São Paulo BEC), rests on a selected subsample, and comes from own project runs.
Follow-ups¶
- Read alongside the decomposition figure and winner-switching evidence that anchor the lost-scale hypothesis; the cell pattern is only one of three supporting strands.
- Probe how sensitive the quantity and fragmentation contrasts are to the definition of the buyer-item-month cell (e.g., quarter rather than month).