Appendix
A1. Data Construction and Scope
- Analysis window: 2015-2025.
- District-year panel size: 143 rows (13 districts x 11 years).
- Primary identifiers:
api_norm, district, year.
- Border geometry includes TX-MX plus TX-NM, TX-OK, TX-LA boundary proximity.
Build validation counts
| Metric |
Value |
| Wells loaded |
1,010,432 |
| Inspections (2015-2025) |
1,867,859 |
| Violations (2015-2025) |
191,762 |
| Border-exposed wells (any 50 km border) |
169,520 |
| Panel observations |
143 |
| Districts |
13 |
Border subtype counts (50 km)
| Border subtype |
Wells |
| TX-MX |
40,339 |
| TX-NM |
81,567 |
| TX-OK |
19,643 |
| TX-LA |
29,675 |
A2. Supplementary Equations
Border-type FE interaction model
Y_{dt} = \alpha_d + \gamma_t + \sum_k \lambda_k(Post2019_t \times Type_{kd}) + \sum_k \phi_k(PostTrend_t \times Type_{kd}) + \varepsilon_{dt}
where k \in \{\text{TX-MX}, \text{TX-NM}, \text{TX-OK}, \text{TX-LA}\}.
Continuous exposure FE interaction model
Y_{dt} = \alpha_d + \gamma_t + \eta_1(Post2019_t \times ShareBorder_{dt}) + \eta_2(PostTrend_t \times ShareBorder_{dt}) + \varepsilon_{dt}
Cutoff-specific exposure
ShareBorder^{(c)}_{dt}, \quad c \in \{25,75,100\}
substituted into the same FE interaction framework.
A3. Main FE Interaction Table (RQ2)
| Outcome |
post_2019 x border |
p-value |
post_trend x border |
p-value |
N |
| inspection_intensity |
-0.1191 |
0.0753 |
-0.0052 |
0.8181 |
143 |
| violations_per_inspection |
0.0040 |
0.8881 |
-0.0012 |
0.8350 |
143 |
| avg_days_to_enforcement |
-74.5893 |
0.0156 |
-1.1587 |
0.9252 |
143 |
| resolution_rate |
0.0404 |
0.4520 |
-0.0186 |
0.3404 |
143 |
A4. Border-Type Timing Interactions (Money Plot Companion)
| Term |
Coefficient |
p-value |
| post_2019:has_tx_mex |
4.0900 |
0.9062 |
| post_2019:has_tx_nm |
-18.7442 |
0.6013 |
| post_2019:has_tx_ok |
-14.2446 |
0.8134 |
| post_2019:has_tx_la |
-43.6598 |
0.6415 |
| post_trend:has_tx_mex |
-0.0148 |
0.9991 |
| post_trend:has_tx_nm |
22.9067 |
0.0189 |
| post_trend:has_tx_ok |
-16.7188 |
0.0794 |
| post_trend:has_tx_la |
0.6415 |
0.9551 |
A5. Continuous Exposure Results
| Family |
Outcome |
Term |
Coef |
p-value |
N |
| RQ1 levels continuous |
inspection_intensity |
share_border_exposed_insp |
0.2095 |
0.4757 |
143 |
| RQ1 levels continuous |
avg_days_to_enforcement |
share_border_exposed_insp |
103.4683 |
0.5710 |
143 |
| RQ1 levels continuous |
violations_per_inspection |
share_border_exposed_insp |
-0.1585 |
0.0144 |
143 |
| RQ1 levels continuous |
resolution_rate |
share_border_exposed_insp |
-0.0420 |
0.8619 |
143 |
| RQ2 FE continuous |
avg_days_to_enforcement |
post_2019:share_border_exposed_insp |
-109.4067 |
0.4449 |
143 |
| RQ2 FE continuous |
avg_days_to_enforcement |
post_trend:share_border_exposed_insp |
13.9623 |
0.7415 |
143 |
| RQ2 FE continuous |
resolution_rate |
post_2019:share_border_exposed_insp |
-0.0322 |
0.8163 |
143 |
| RQ2 FE continuous |
resolution_rate |
post_trend:share_border_exposed_insp |
-0.0979 |
0.0423 |
143 |
A6. Cutoff Sensitivity (Timing-Focused Terms)
| Cutoff km |
Term |
Coef |
p-value |
N |
| 25 |
post_2019:share_border_25km |
-101.9283 |
0.7010 |
143 |
| 75 |
post_2019:share_border_75km |
-75.6591 |
0.5116 |
143 |
| 100 |
post_2019:share_border_100km |
-4.4795 |
0.9474 |
143 |
A7. District Border-Type Profile
| District |
Wells |
Dominant type |
TX-MX share |
TX-NM share |
TX-OK share |
TX-LA share |
| 01 |
31,898 |
TX-MX |
0.2313 |
0.0000 |
0.0000 |
0.0000 |
| 02 |
17,099 |
NONE |
0.0000 |
0.0000 |
0.0000 |
0.0000 |
| 03 |
16,700 |
TX-LA |
0.0000 |
0.0000 |
0.0000 |
0.1166 |
| 04 |
20,973 |
TX-MX |
0.6384 |
0.0000 |
0.0000 |
0.0000 |
| 05 |
9,938 |
TX-OK |
0.0000 |
0.0000 |
0.0022 |
0.0000 |
| 06 |
24,422 |
TX-LA |
0.0000 |
0.0000 |
0.0293 |
0.5235 |
| 08 |
105,931 |
TX-NM |
0.0001 |
0.1905 |
0.0000 |
0.0000 |
| 09 |
46,485 |
NONE |
0.0000 |
0.0000 |
0.0000 |
0.0000 |
| 10 |
29,621 |
TX-OK |
0.0000 |
0.0009 |
0.3020 |
0.0000 |
| 6E |
6,235 |
NONE |
0.0000 |
0.0000 |
0.0000 |
0.0000 |
| 7B |
21,230 |
NONE |
0.0000 |
0.0000 |
0.0000 |
0.0000 |
| 7C |
43,061 |
NONE |
0.0000 |
0.0000 |
0.0000 |
0.0000 |
| 8A |
42,005 |
TX-NM |
0.0000 |
0.4182 |
0.0000 |
0.0000 |
A8. Figures and Output Artifacts
- Border exposure map:
analysis/output_borderlands/well_border_exposure_map.png
- Border vs non-border trends:
analysis/output_borderlands/border_vs_nonborder_trends.png
- Main timing figure:
analysis/output_borderlands/money_plot_timing_border_prepost2019.png
- Timing CI table:
analysis/output_borderlands/money_plot_timing_ci_by_year.csv
A9. Optional Prior Artifact (Not Estimated in Current Causal Scope)
analysis/output_borderlands/competition_asymmetry_results.csv contains:
gap_pos = 0.5837 (p < 0.001)gap_neg = 0.4993 (p = 0.0027)
These estimates are not part of the current notebook's identified model scope and should not be interpreted as a completed reaction-function test in this manuscript version.
