# Appendix B — Data construction decisions Every data-construction decision in this paper was made to fit the NYC 311 Socrata endpoint, the NYC DSNY policy schedule, and the factor-factory `Panel` contract. This appendix documents the decisions that affect the identification strategy or the interpretation of the ATT, so a city staffer replicating the work can audit each choice independently. ## B.1 Geography: why community district (CD) **Alternatives considered.** Census tract (~2,300 in NYC), census block group (~7,000), ZIP code (~180), borough (5), police precinct (~77). **Why CD.** The 311 Socrata endpoint attaches a `community_board` string directly to every complaint; we do not have to geocode latitude/longitude against tract polygons, which would introduce geocoding-failure noise and a nontrivial dependency on `nyc-geo-toolkit`. The containerization rule applies at the building level, but the *policy-decision unit* is the community district — DSNY organizes enforcement and compliance reporting at the CD level, not at the tract or block level. Matching the identification strategy's geographic unit to the policy-decision unit avoids an unnecessary aggregation step. **What this costs.** CDs are politically-drawn boundaries spanning ~100k residents each, so within-CD heterogeneity in residential vs. commercial mix, baseline rat ecology, and built-environment characteristics is substantial. A building-level or block-level analysis would give sharper identification; we note the trade-off in §5.3 of the main manuscript and flag building-level replication (via DOB permit + DOF valuation data) as future work. ## B.2 Time window: 2020-01-01 through 2026-03-31 **Choice of start date.** 2020-01-01 captures roughly three years of pre-pilot data (2020-01 through 2023-06), which is the maximum reasonable pre-period to balance against the 33-month post-window for the pilot cohort. Going further back (2018–2019) would introduce pre-COVID level differences that the CD × month fixed effects can absorb but which make the pre-trend visual in Figure 1 harder to interpret. **Choice of end date.** 2026-03-31 is the most recent quarter available at the time of manuscript finalization. The citywide cohort needs as much post-window as we can give it; the 16.5-month post-window in the current panel is thin but workable. A follow-up paper with two more years of data would substantially tighten the citywide-cohort CIs. **Why we combined the 2020-2024 and 2025-2026 fetches.** The Socrata `bulk_fetch` utility issues independent per-borough calls per date range; we fetched in two slices (2020–2024 ten months ago, 2025–2026 for this revision) because the 2025 records were still being ingested by NYC Open Data during the original run. The notebook 01 pipeline concatenates both slices, deduplicates on `complaint_id`, and emits a single balanced CD × month panel. ## B.3 Frequency: why monthly **Alternatives considered.** Daily, weekly, monthly, quarterly. **Why monthly.** The containerization rule's enforcement is monthly (DSNY cites, processes, and follows up on a monthly cycle; the compliance KPIs DSNY publishes are monthly aggregates). Monthly aggregation also keeps the panel size manageable (5,550 cells) and the CD-level monthly complaint mean large enough (30.3 complaints per CD-month averaged across pre-treatment treated units, and meaningful variance even in the lowest-volume CDs) to support large-sample inference. Daily or weekly aggregation would introduce substantial day-of-week seasonality (Monday complaints are higher than Sunday complaints, and the weekday-weekend mix drifts with month-of-year) without improving identification; quarterly aggregation would cost us event-study granularity without buying anything. ## B.4 Treatment-schedule spec (`rat_mitigation_events_2023.json`) The spec maps every community district to an event date (if treated) or leaves it absent (if never-treated). The schedule has three cohorts in total: **Cohort 1 — Pilot, 2023-07-01**. Nine lower-Manhattan CDs: MN 01–09. Source: [NYC DSNY (2023)](../../MANUSCRIPT.md#ref-nyc2023) press release dated 2023-06-15; rule effective 2023-07-01. **Cohort 2 — Citywide residential 1–9 units, 2024-11-12**. Fifty remaining "standard" CDs: BX 01–12, BK 01–18, MN 10–12, QN 01–14, SI 01–03. Source: [NYC DSNY (2024)](../../MANUSCRIPT.md#ref-nyc2024) agency policy brief dated 2024-10-01; 16 RCNY Chapter 1 rule effective 2024-11-12. This is the first date on which residential buildings citywide were required to containerize; subsequent phases applied to larger building categories but are either outside our panel window or partially covered at the margin. **Never-treated — 15 "irregular" CDs**. Airports (JFK = QN 82, LGA = QN 81), parks (Floyd Bennett Field = QN 84, Randall's Island = MN 64, Prall's Island = SI 95), cemeteries (Green-Wood = BK 55), BoE-only districts (BX 26–28), and Unspecified geocoding-failure rows (five per borough). These CDs are irregular by construction — the rule is not applicable to non-residential / non-commercial land use. Treating them as never-treated is defensible rather than arbitrary. ## B.5 Outcome: `complaint_count` The `complaint_count` column in the `PanelDataset` is the raw count of 311 Rodent service requests with `created_date` in the cell's month. No normalization by population or land area. **Why not per-capita?** The CD × month fixed effects absorb any time-invariant population differences. Per-capita scaling would introduce division by a noisy ACS population estimate and would not change the within-CD identifying variation. The 311 pipeline in this paper is designed around raw counts specifically. **Why not `complaints_per_1000_residents`?** Same reasoning; plus the "per 1000 residents" transform is undefined for the 15 never-treated irregular CDs (airports have zero residents), and dropping those CDs removes the control pool. ## B.6 Reporting-propensity adjustment: none, and why We do NOT adjust the outcome for reporting propensity (e.g., by normalizing rat complaints by total 311 complaints in the cell). Two reasons: 1. The CD fixed effects absorb time-invariant reporting differences. 2. The time fixed effects absorb citywide drift in reporting propensity (e.g., if NYC residents file more of every type of complaint in 2024 than in 2020, the $\gamma_t$ terms capture that). What the fixed effects *cannot* absorb is a reporting-propensity change that correlates with treatment — if containerization makes residents feel the city is responsive and they file more complaints, that's a negative bias against finding an effect. We discuss this in §5.3 of the main manuscript. ## B.7 The 377,950 → 224,889 sample-size correction An earlier draft of this paper reported 377,950 total Rodent complaints; this draft reports 224,889. The discrepancy is a cache- loading bug that crept into notebook 01 across two iterations: 1. The `bulk_fetch` utility caches Socrata fetches by `{borough}_{topic}_{start}_{end}_{page_size}.csv`. An early fetch had been done for the 2020–2021 slice *separately* (different end-date in the filename); a later fetch for the 2020–2024 slice overlaid the same borough-topic but with a wider window. 2. Notebook 01's record-loading loop globbed `*_rodent_*.csv` and concatenated everything, double-counting the overlapping 2020–2021 period. 3. The result was a sample size inflated by roughly the 2020–2021 contribution — 377,950 observed vs. the true 224,889. The fix was to purge the stale 2020–2021 cache files (they're redundant given the 2020–2024 superset) and to add a deduplication pass in the cache-loader. The record count in the current paper is the deduplicated figure. **This has negligible effect on the ATT estimates themselves** because duplicated observations uniformly inflate both treated and control cells, so the DiD coefficient is largely unchanged. What changed are the panel-summary statistics (total complaints, per-CD-month means) and — by extension — the reporting-propensity discussion in §5.3. ## B.8 What's in `data/cache/` and what isn't **Committed to git**: `data/rat_mitigation_events_2023.json` (the treatment schedule) and `data/README.md` (this appendix's precursor). **Gitignored**: `data/cache/*.csv` (raw Socrata responses), the `.jellycell/cache/` directory (jellycell's manifest store), and `site/` (the jellycell-rendered HTML catalogue). The raw CSV cache would add ~85 MB to the repo and is trivially reconstructable via the `nyc311.pipeline.bulk_fetch()` call in notebook 01's first cell. A reader attempting to reproduce the analysis starts from `pnpm showcase:run showcase-rat-containerization`, which runs all 10 notebooks in order and fetches the underlying data from NYC Open Data on first pass (~15 minutes over Socrata) and from the local cache on subsequent runs (~30 seconds).