International Bancshares Corporation (NasdaqGS:IBOC) (IBOC)

Announcement

—

First SEC disclosure

Meeting / Vote

—

ADOPTED_THEN_RESCINDED

Effective

—

Legal effective date

Market Cap

$4.8B

At announcement

Why this firm matters

Standard cohort firm (Adopted_Then_Rescinded). Included for breadth across destinations and sectors.

Controller & ownership

Diffuse / non-controlled

Ownership concentration data not yet documented for this firm.

Vote outcome — reincorporation proposal

Approval standard: N/A. 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 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. International Bancshares Corporation (NasdaqGS:IBOC) 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.

Source filings pending EDGAR backfill. No primary-source filings are presently linked in the canonical record for this firm. Until backfill completes, see SEC EDGAR company browse (CIK 0000315709) → for the live filings list.

Classification & audit trail

Bucket

ADOPTED_THEN_RESCINDED

Panel eligibility

PANEL_A_TX_INCUMBENT

Audit status

PANEL_A_TIER

Source confidence

PANEL_A_INCLUSION

Transaction status

N/A

Audit notes

[2026-04-30] v3.84-rev5y: Inserted as Panel A (TX-incumbent universe) reference firm. Source: panelA_TX_incumbent_universe_v2.3_FULL.csv. NOT a DE→TX migrator. Eligible for the §21.552 adopter cohort analysis (see luv_case_study.html Section M.2 for the full TX-incumbent roster).
PATCHED_rev131-phase-a-tboc-21552-adopters-2026-06-04_phase_a: tboc_21_552_tier=TIER_0_RESCINDED acc=0001104659-25-076591
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.
[2026-06-11] Reclassified INCUMBENT -> ADOPTED_THEN_RESCINDED per Shane. Adopted SB29 § 21.552 3% derivative threshold + Texas Business Court (Fourth Business Court Division) exclusive forum + jury-trial waiver via Second Amended & Restated Bylaws effective 2025-08-06 (8-K filed 2025-08-12, acc 0001104659-25-076591); rescinded ALL THREE via Third Amended & Restated Bylaws effective 2026-05-12 (8-K acc 0001104659-26-059135). Not a state change. panel_a/panel_b set 0.