Announcement
—
First SEC disclosure
Meeting / Vote
—
TX_INCUMBENT_21_552_ADOPTER
Effective
—
Legal effective date
Market Cap
$18.0B
At announcement
Why this firm matters
Mid-to-large-cap firm ($18.0B) with sufficient market depth for reliable event-study identification.
Controller & ownership
Diffuse / non-controlledDiffuse institutional + activist (Elliott Investment Management) holds approximately 9.6% of voting power. No single holder reaches the controlled-company threshold (>50% of voting power).
Source: DEF 14A 2026 (filed 2026-03-27); Schedule 13G/A filings
Vote outcome — reincorporation proposal
Approval standard: Board approval; bylaws amendment under TBOC §21.057. Meeting type: annual.
Vote totals not yet pulled. Awaiting EDGAR Item 5.07.
Event-study abnormal returns — announcement window
Returns around the announcement date.
No announcement-window CARs available for this firm yet.
Event-study abnormal returns — vote window
Returns around the shareholder-vote (or written-consent) date.
No vote-window CARs available for this firm yet.
Long-run abnormal returns & pooled estimates
Buy-and-hold abnormal returns (1 / 3 / 6 / 12 months) and calendar-time portfolio alpha (CTE) post-effective.
No long-run / pooled estimates available for this firm yet — run phase5z_compute_longrun.py on Windows to populate (requires effective date ≥ 3 months ago).
Cohort-level robustness battery
Heckman selection-corrected ATE · Romano-Wolf step-down + BH FDR · pooled BHAR. This firm's reading is shown in context of the full cohort.
Heckman two-step selection correction (controlled-vs-widely-held)
Cohort ATE = +0.94% (SE = 7.06%, n = 2395) after correcting for controller-status selection (inverse Mills ratio = -0.062).
Romano-Wolf step-down + Benjamini-Hochberg FDR (n = 47)
This firm: per-firm adjusted p-values pending. Multiple-hypothesis correction is computed across the full cohort to control family-wise error rate at alpha = 0.05.
Pooled cohort BHAR (mover firms only)
BHAR_63d: mean = -5.60% (SE = 22.11%, n = 3, p = 0.499) · BHAR_126d: mean = +17.33% (SE = 41.17%, n = 3, p = 0.774)
See Cohort event study → for the full battery and forest plots.
Texas statutory-adoption event study (SB 29 dates & bylaw amendments)
Event-study readings around the SB 29 legislative milestones and this firm's §21.552 bylaw-amendment date. Each panel shows the day-0 abnormal return under multiple specifications, plus long-run BHAR. Run via
02_BESPOKE/statutory_events_runner.py.LUV 21 552 next trade 2025 05 20T0 = 2025-05-20
Headline T0: next trading day after 8-K filing (after-market-close rule)
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | +0.09% | Patell-z p-value = 0.964 |
| Sector-augmented (SPY + JETS airline ETF) | +0.46% | Patell-z p-value = 0.785 |
| Synthetic control (8-donor airline peer pool) | +0.20% | no inference |
| Robustness footnote: SPY + XLI | +0.15% | Patell-z p-value (footnote spec) = 0.939 |
| Robustness footnote: SPY + USO | +0.08% | Patell-z p-value (footnote spec) = 0.967 |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | -3.33% | n = 22 days |
| 3 months vs SPY | -11.37% | n = 64 days |
| 6 months vs SPY | -12.42% | n = 127 days |
Alternative T0 specifications ▾
| T0_a_board_2025-05-16 | +1.77% | p = 0.391 |
| T0_b_filing_2025-05-19 | -0.42% | p = 0.837 |
| T0_c_next_trading_2025-05-20 | +0.09% | p = 0.964 |
Cumulative abnormal returns by window ▾
| Window | n days | CAR | p |
| Day0 | 1 days | +0.09% | p = 0.964 |
| CAR_-1_+1 | 3 days | -0.61% | p = 0.863 |
| CAR_-2_+2 | 5 days | -0.64% | p = 0.888 |
| CAR_-5_+5 | 11 days | +3.89% | p = 0.567 |
| CAR_-10_+10 | 21 days | -0.19% | p = 0.984 |
| Post_+0_+5 | 6 days | +2.30% | p = 0.647 |
| Post_+0_+20 | 21 days | -4.77% | p = 0.611 |
| Post_+0_+60 | 61 days | -12.78% | p = 0.424 |
Calendar-time portfolio alpha (post-event): annualized = +14.17% · t = +0.31 · p = 0.757 · n = 12 months
SB29 senate passage 2025 04 03T0 = 2025-04-03
Senate engrossment (RV#159); passage near-certain in Senate
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | -6.18% *** | Patell-z p-value = 0.005 |
| Sector-augmented (SPY + JETS) | -2.96% * | approx Patell-z p-value (2-factor) = 0.076 |
| Matched pair vs DAL (market-model-adjusted) | -1.48% | two-sided p-value = 0.610 |
| Raw differential vs DAL | +1.48% | no inference |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | -0.77% | n = 21 days |
| 3 months vs SPY | +1.84% | n = 63 days |
| 6 months vs SPY | -11.44% | n = 126 days |
| 12 months vs SPY | +9.63% | n = 252 days |
SB29 house passage 2025 05 02T0 = 2025-05-02
House RV#1339; passage near-certain in both chambers (cleanest single-day milestone)
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | +2.55% | Patell-z p-value = 0.220 |
| Sector-augmented (SPY + JETS) | +0.10% | approx Patell-z p-value (2-factor) = 0.952 |
| Matched pair vs DAL (market-model-adjusted) | -1.59% | two-sided p-value = 0.595 |
| Raw differential vs DAL | -1.96% | no inference |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | +4.04% | n = 21 days |
| 3 months vs SPY | -11.45% | n = 63 days |
| 6 months vs SPY | -18.37% | n = 126 days |
SB29 signed effective 2025 05 14T0 = 2025-05-14
Signed by Governor; effective immediately
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | +0.11% | Patell-z p-value = 0.957 |
| Sector-augmented (SPY + JETS) | +2.15% | approx Patell-z p-value (2-factor) = 0.199 |
| Matched pair vs DAL (market-model-adjusted) | +4.92% | two-sided p-value = 0.107 |
| Raw differential vs DAL | +4.94% | no inference |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | -0.49% | n = 21 days |
| 3 months vs SPY | -11.69% | n = 63 days |
| 6 months vs SPY | -9.51% | n = 126 days |
LUV 21 552 board 2025 05 16T0 = 2025-05-16
Board adoption of Fifth Amended and Restated Bylaws (§21.552 election); 8-K acc 0000092380-25-000119
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | +1.76% | Patell-z p-value = 0.394 |
| Sector-augmented (SPY + JETS) | +1.54% | approx Patell-z p-value (2-factor) = 0.360 |
| Matched pair vs DAL (market-model-adjusted) | +1.42% | two-sided p-value = 0.642 |
| Raw differential vs DAL | +1.28% | no inference |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | -4.33% | n = 21 days |
| 3 months vs SPY | -12.19% | n = 63 days |
| 6 months vs SPY | -12.13% | n = 126 days |
LUV 21 552 filing 2025 05 19T0 = 2025-05-19
8-K filed AFTER market close at 16:38:57 ET
| Specification | Day-0 AR | Inference |
|---|---|---|
| Market model (SPY benchmark) HEADLINE | -0.40% | Patell-z p-value = 0.845 |
| Sector-augmented (SPY + JETS) | -0.41% | approx Patell-z p-value (2-factor) = 0.807 |
| Matched pair vs DAL (market-model-adjusted) | -0.84% | two-sided p-value = 0.783 |
| Raw differential vs DAL | -0.77% | no inference |
Long-run BHAR after this event (1 / 3 / 6 / 12 months) ▾
| 1 month vs SPY | -4.27% | n = 21 days |
| 3 months vs SPY | -10.39% | n = 63 days |
| 6 months vs SPY | -13.70% | n = 126 days |
Texas Statutory Adoptions
Status: N/A pending reincorporation.
The Texas opt-in statutory regimes (TBOC §21.552 / SB 29 derivative threshold; TBOC §21.373 / SB 1057 shareholder-proposal threshold) are available only to firms that are nationally listed Texas corporations. Southwest Airlines Co. is not yet Texas-incorporated; the move is pending shareholder vote with a proposed effective date of TBD. These adoptions can be elected only on or after the firm's TX effective date.
Source filings
Primary-source documents on SEC EDGAR plus IR / search links.
Classification & audit trail
Bucket
COMPARATOR_TX_INCUMBENT
Panel eligibility
PANEL_C_TX_INCUMBENT_ADOPTER
Audit status
VERIFIED_EDGAR
Source confidence
VERIFIED_PRIMARY_SOURCE
Transaction status
N/A
Audit notes
[2026-04-30] v3.84-rev5x: LUV added as a TX-INCUMBENT 21.552 ADOPTER comparator (distinct from the DE->TX migrator cohort). Bespoke event-study battery from 02_BESPOKE/LUV_TBOC_21552_Analysis/luv_event_study_results.json + bespoke statutory-events runner output. Board adoption 2025-05-16, 8-K filing 2025-05-19 (after market close), T0 headline 2025-05-20, accession 0000092380-25-000119, Items 3.03/5.03/9.01.
Related firms
Use these for cross-firm sanity checks — peers in size, sector, or destination.
Replication kit — downloads
Every numerical result on this page traces to one of the files below. Southwest Airlines is benchmarked first against airline peers (Delta, United, American, and six others), then against the S&P 500 and the JETS industry ETF as secondary controls. Peer-anchored inference is the project standard: peer comparison is the primary test, market index is the secondary check. A reviewer who runs the script in their language of choice and matches expected_results.json within the documented tolerances (±0.5 percentage points on point estimates, ±0.05 on p-values) has independently validated the methodology.
Data files
CSV
Daily prices
Daily closing prices for Southwest Airlines (LUV) plus eight airline peer firms (American/AAL, Delta/DAL, United/UAL, Alaska/ALK, JetBlue/JBLU, Allegiant/ALGT, SkyWest/SKYW, Ryanair/RYAAY), the S&P 500 (SPY) and NASDAQ-100 (QQQ) market benchmarks, and the JETS airline-industry ETF over the 2020-2026 window. The only raw input the analysis needs.
518 KB
Download ↓
CSV
Day-0 + CAR table
Compact summary table: one row per (specification, window) pair. Includes the two flagship specifications (market model and augmented SPY+JETS), all multi-window CARs (-1/+1, -2/+2, -5/+5, -10/+10), and post-event windows (0/+5, 0/+20, 0/+60). Day-0 ARs plus p-values.
<1 KB
Download ↓
JSON
Full results
The complete machine-readable output: market model + augmented results, three matched-pair tests (vs Delta, United, American), eight peer-BHAR comparisons, synthetic control donor weights, BHAR horizons (1/3/6/12 month), calendar-time portfolio alpha, robustness diagnostics.
18 KB
Download ↓
JSON
Reference output
The published v1.0 numbers, frozen. Diff your replication against this to verify you produced the same answer within the documented tolerances.
18 KB
Download ↓
MD
Bespoke report
The original bespoke analysis report written when the analysis was first conducted (April 2026). Includes methodology, narrative interpretation of the null finding, and the project-lead's editorial commentary on what the result means for the SB 29 reform package.
6 KB
Download ↓
Code & documentation
.py
Python replication
Self-contained Python script running all six specifications from the daily prices file: market model, augmented (S&P + JETS), three matched-pair tests, and synthetic control. About 700 lines (the original bespoke implementation; richer than the XOM kit's Python). Standard libraries (pandas, numpy, scipy, statsmodels). 10 minutes end-to-end.
30 KB
Download ↓
.R
R replication
R port of the core six specifications using quadprog for the synthetic-control simplex problem. Produces output_R.json in the same schema as the Python version for cross-platform verification.
7 KB
Download ↓
.do
Stata replication
Stata port: market model, augmented, three matched-pair tests, and the pre-event drift placebo F-test. Requires synth, mat2txt, estout packages. Use this version when peer-review reviewers want the analysis in their preferred language.
8 KB
Download ↓
txt
Python requirements
Pinned package versions for the Python replication. Use with
pip install -r requirements.txt to recreate the exact environment the published numbers were computed in.MD
README guide
Run instructions, tolerance rules, methodology summary, the peer-anchoring rationale (why this kit tests against Delta/United/American before testing against the market), and the protocol for reporting your replication findings back to the project lead.
8 KB
Download ↓
Primary sources — SEC EDGAR
EDGAR
8-K filing (May 19, 2025)
Form 8-K Item 5.03 in which Southwest Airlines disclosed its board's adoption of the TBOC §21.552 3%-derivative-suit ownership-threshold bylaw amendment. Filed 2025-05-19; this is the trigger for the event-window analysis.
EDGAR
Bylaws Ex. 3.1
Exhibit 3.1 to the 8-K above — Fifth Amended and Restated Bylaws of Southwest Airlines Co., showing the full text of the §21.552 election. Article VI, Section 6.07 contains the 3% ownership-threshold language.
Headline to verify. Day-0 abnormal return for Southwest Airlines on the trading day after its TBOC §21.552 8-K filing = +0.09% (Patell-z p = 0.96). The matched-pair tests vs Delta, United, and American all return p > 0.7. The augmented model (S&P 500 + JETS industry ETF) returns Day-0 = +0.46% (p = 0.78). Twelve-month BHAR against the market is statistically indistinguishable from zero. The market did not price a §21.552 governance discount on Southwest Airlines — at any of the four single-firm specifications, against any of the airline peers, or in the long run.
← Back to The Reincorporation Tracker · Cohort event study · JSON for LUV