GetCoattail Research — The Filing Tape #144. Amkor Technology has been one of the most searched-for stocks on Zacks.com lately, and the filings behind that attention describe a register held up by almost nobody we track: 1 of the 147 superinvestors held the stock at June 30, 2026 — a new position of 8,860 shares — while insiders recorded no purchase at all in the last year, against 41 sales. The register's real weight sits elsewhere, in a founding family's SC 13D group whose largest single row prints 33.7%.
The Hype
Amkor's attention is search-driven. Zacks reported on October 20, 2026 that the stock "has recently been on Zacks.com's list of the most searched stocks," with shares returning −19.7% over the past month against +0.7% for the Zacks S&P 500 composite, while the Zacks Electronics - Semiconductors industry lost 11.7%, and the current-quarter consensus estimate stands at $0.79 per share, up 54.9% from a year earlier, with the consensus unchanged over the last 30 days and the fiscal-year consensus at $2.60. Zacks Our price file adds the longer path: Amkor rose 91.5% in the second quarter, from $45.03 on March 31 to $86.23 on June 30, then fell back to $56.02 by October 2 — down 35.0% from the quarter-end close, up 41.9% year to date, up 89.0% from a year ago and 40.1% below its 252-session high close of $93.55, set on June 22, 2026. A chip-packaging name that nearly doubled in a quarter and then gave back a third of the peak: the filings answer who holds it, and what insiders have done.
The Tape
For Amkor — the one hundred and forty-fourth Filing Tape audit — the tape shows a tracked register with a single, brand-new holder, a full market that added 132 filers, an insider record with a full year of sales and no purchases, no congressional row at all, a 5% register dominated by a founding family's 13D group, and a borrow that just set its series peak.
| Lens | As of | What the filings show | Direction vs prior period |
|---|---|---|---|
| Superinvestors (13F) | Jun 30, 2026 | 1 holder of 147 tracked managers holds 8,860 shares; the position is new | 1 new; 0 continuing; 0 exited |
| All institutions (13F) | Jun 30, 2026 | 650 filers; 115,970,374 shares; reported value $9,887,576,384 | Filers +132; shares +9.82%; reported value +110.57% |
| Insiders (Form 4) | Oct 2, 2026 | Last 90 days: 0 purchases and 9 sales; last year: 0 purchases and 41 sales | Sales of $3,974,597.00 in 90 days against no purchases |
| Congress | Oct 3, 2026 | No row in the combined, House or Senate aggregates | None recorded |
| 13D/G | May 5, 2026 | 5 parsed filings (3 SC 13D family, 2 SC 13G family); register maximum 33.7% | Latest filing May 5, 2026 prints John T. Kim at 30.4%, as of May 1, 2026 |
| Short interest (FINRA) | Sep 15, 2026 | 9,900,880 shares; 2.37 days to cover; 3.99% of the share count | Series peak; up 5.49% from the prior settlement; up 102.9% from a year ago |
Lens 1 — the superinvestors: one holder, and the position is new. We track 149 managers whose 13F portfolios we collect from SEC EDGAR — 147 are in the collection (144 at a June 30 period-end, 3 early filers at September 30, none of them holding this name) — and the June 30, 2026 register is 1 distinct manager holding 8,860 shares worth $763,998, long only, with no option rows: the single row is labelled NEW, there are no continuing holders, and no holder exited during the quarter. Lee Ainslie - Maverick Capital is the register's only holder: 8,860 shares worth $763,998 — 100.0% of the tracked stake — at a 0.01% portfolio weight (filed August 14, 2026). Because the only holder is new, there is no continuing-holder movement to verify; the register itself reconciles with no residual, because the March 31 pipeline register for this CUSIP is empty (0 rows) and the June 30 register is this single row (methodology). The June row implies $86.23, the June 30 close (methodology). 13F figures are as of June 30, 2026, published up to 45 days later.
Lens 2 — institutions: 132 more filers, and a reported value that doubled with the price. At June 30, 2026, 650 institutions reported positions on the name's single CUSIP, up 132 from 518 at March 31 (+25.48%); 644 are long. Reported shares rose 9.82% to 115,970,374 (+10,372,180 shares), and reported value rose 110.57% to $9,887,576,384, labelled "reported" because the aggregate includes option rows (methodology), in a quarter when the price rose 91.5% — the value jump is the share increase compounded by the price move, not a separate fact. Flow counts agree (603 entered, 471 exited, net +132). The single-CUSIP aggregate matches the by-ticker total on every field (methodology), and implies $85.26 against the $86.23 close. Against that total, the tracked cohort's 8,860 shares are 0.01% of reported institutional shares.
Lens 3 — insiders: no purchase in a year, and no officer purchase in the whole record. The parsed Form 4 record holds 238 filings through October 2, 2026. Across the full record there are 10 open-market purchases (6,555,770 shares for $143,243,574.50, by 5 buyers, none of them an officer purchase) against 49 sales (23,069,250 shares for $1,050,525,252.69, by 15 sellers). The last year holds no purchase at all, against 41 sales (20,404,661 shares for $992,160,239.48, by 13 sellers), and the last 90 days hold no purchase, against 9 sales (71,221 shares for $3,974,597.00, by 5 sellers, 6 of them officer sales) — so every purchase in the record is more than a year old, and no officer purchase appears anywhere in it. The sales imply $55.81 per share over the last 90 days, $48.62 over the last year and $45.54 over the full record, and the purchases imply $21.85 — every cited figure sits inside its window's close range (methodology). The site's insider aggregate records the same zero purchases and the same 5 sellers over its own 90-day window, with a different sales count that its later window end explains (methodology).
Lens 4 — Congress: no row in any aggregate. The combined aggregate (as of October 3, 2026), the House aggregate (as of October 3, 2026) and the Senate aggregate (as of October 1, 2026) each carry no row for this name — no purchase and no sale is recorded in any of the three.
Lens 5 — the 5% register: a founding family's 13D group, maximum 33.7%. Our full parse holds 5 SC 13D/G filings matching the site aggregate exactly — 3 SC 13D family and 2 SC 13G family, all five of them amendments; 54 reporter names across 139 rows. The three 13D filings are successive amendments of a single joint filing by the Kim family group — dozens of related individuals, trusts and partnerships reporting together. The maximum is John T. Kim at 83,332,761 shares and 33.7% as of May 14, 2025 (filed May 16, 2025, SC 13D/A). The latest filing, the group's May 5, 2026 amendment, prints John T. Kim at 75,339,103 shares and 30.4% as of May 1, 2026. The 13G side is two lines: Dimensional Fund Advisors LP at 10,991,469 shares and 4.4% as of March 31, 2026, and The Vanguard Group at 0 shares and 0.0% as of March 13, 2026.
Lens 6 — short interest: a series peak at the latest settlement. The latest FINRA settlement, September 15, 2026, records 9,900,880 shares sold short at 2.37 days to cover — the highest reading in all 137 settlements, up 5.49% from the prior settlement — 3.99% of the share count in our fundamentals file (dated April 21, 2026). The latest reading is also 11.9% above the June 30, 2026 settlement (8,847,679 shares) and 102.9% above the year-ago settlement (4,880,707 shares on September 15, 2025); the series minimum is 2,016,659 shares, set on October 13, 2023. The recent path runs 8,847,679 (June 30), 8,672,282 (July 15), 8,926,978 (July 31), 9,634,298 (August 14), 9,385,236 (August 31) and 9,900,880 (September 15) — two dips inside a climb that ends at the peak. No step in the full series reaches 2x or falls to one-half (methodology).
The Gap
The narrative arriving this week is a search-and-estimates one: a most-searched packaging name whose current-quarter consensus has risen 54.9% year over year, inside an industry down 11.7% in a month, on a stock that rose 91.5% in the second quarter and has since fallen 35.0% from the quarter-end close. The June tape describes sponsorship that is broad in the full market and nearly absent in the tracked cohort. Institutions added 132 filers and 9.82% more shares, but the 147 tracked managers hold exactly one position — new, 8,860 shares, a 0.01% portfolio weight — which is 0.01% of the shares institutions report. The insider lens is one-sided in the other direction: no purchase in a year, no officer purchase in the entire parsed record, and $992,160,239.48 of sales in the last year alone. The register's concentration is not institutional at all: it is the Kim family group's 13D, whose largest single row prints 33.7% and whose latest amendment prints 30.4%. Against all of that, the borrow has climbed to its series peak, more than double its year-ago level. One plausible reading is that the filings describe a stock whose register is anchored by its founding family and a widening institutional tail, while the tracked managers, the insiders and the shorts each stand somewhere else.
What Would Change the Picture
Nothing above is a recommendation. These filings would change it:
- 1. The 2026Q3 13F season (filing window closing mid-November 2026). The tracked baseline is 1 June holder with 8,860 shares, labelled NEW. Whether Lee Ainslie - Maverick Capital holds, adds to or exits that position, and whether any second tracked manager appears, would each change this lens.
- 2. A first insider purchase in more than a year. The parsed record holds 10 purchases against 49 sales, with no purchase in the last year and no officer purchase at all. Any purchase in the next window would be the first in over a year; continued sales alone would extend the one-sided pattern into a second year.
- 3. A first congressional transaction. The combined, House and Senate aggregates record no transaction at all. Any recorded purchase or sale in either chamber would change this lens from blank to a first line.
- 4. A new family-group amendment, or a passive print above 4.4%. The register's 5 filings are all amendments, its 13D maximum is John T. Kim at 33.7% as of May 14, 2025, and its latest amendment prints 30.4% as of May 1, 2026. A further group amendment moving that row, or any new 13G print above Dimensional Fund Advisors LP's 4.4%, would change this lens.
- 5. Short interest below the September 15 peak, or a new peak above it. The borrow stands at its series peak of 9,900,880 shares. A reading below 9,900,880 would end the climb at one peak settlement; a reading above it would extend the record to two straight settlements.
Related reading: Five of 147: Two New Positions Are 90.5% of the Superinvestors' Aptiv Stake. Its Insiders Bought $8.25 Million in 90 Days.; Fifteen of 147: One Holder Is 30.0% of the Superinvestors' Pfizer Stake. Its Insiders Bought $2.96 Million in 90 Days.. Amkor's own page: Amkor Technology (AMKR) on GetCoattail.
Methodology and data notes
- As-of & limits: The lenses rest on different clocks, none live: 13F is a June 30, 2026 snapshot published up to 45 days later; Form 4 runs through October 2, 2026; Congress aggregates run through October 3, 2026 (Senate through October 1, 2026); 13D/G through May 5, 2026; short interest through September 15, 2026; the price file ends October 2, 2026. Seven limits are specific to this audit. First, the roster expanded before the recent audits — from 85 managers (83 filing) to 149 (147 filing) — so "of 147" counts are not comparable to earlier pieces' "of 83" figures. Second, this name carries a single CUSIP (031652100), and the full-market by-CUSIP row matches the by-ticker aggregate on every field — holders, long holders, shares, reported value, prior holders and prior reported value — so no CUSIP blending question arises. Third, the tracked register reconciles exactly: the March 31 pipeline register holds no row for this CUSIP (0 shares) and records no exit, and the June 30 register (8,860 shares) is the single NEW row itself, with no residual in either quarter and no leftover Q2 pipeline row. No September 30, 2026 early filer holds this name, and because the only June holder is new, there are no continuing holders whose quarter-to-quarter movement could be verified row by row. Fourth, every insider figure cited sits inside its window's close range (90-day sales imply $55.81 against a $42.73–$72.16 close range; one-year sales $48.62 and full-record sales $45.54 and purchases $21.85 against their window ranges; the 90-day and one-year windows record no purchase, so no purchase figure exists to test there). The site's 90-day insider aggregate (dated October 21, 2026) records 0 purchases, 7 sales worth $3,579,087.00 and 5 sellers, against the full parse's 90 days to October 2, 2026 of 0 purchases, 9 sales worth $3,974,597.00 and 5 sellers: the two windows end on different dates, so the counts are reported side by side as recorded, and neither is treated as an error in the other. Fifth, the 5% register's cross-date share total of 928,106,871 is an arithmetic sum of reporter rows across different as-of dates, not a current combined stake: it counts the Kim family group's joint filing once per reporting entity across three successive amendments (44 to 49 rows per filing), alongside Dimensional Fund Advisors LP at 10,991,469 shares (March 31, 2026) and The Vanguard Group at 0; at about 3.7 times the company's 247,872,518 shares outstanding, the sum cannot be a stake. Parsed totals match the aggregates exactly. Sixth, the short-interest series carries no step of 2x or more and no step to one-half or less (largest step 1.741x at the February 26, 2021 settlement; smallest step 0.618x at the July 15, 2024 settlement), no row carries a split flag, one row carries a FINRA revision flag (June 15, 2021), and our price file records no split entries for this name, so settlements across the full series are compared directly. The issuer-name field reads "Amkor Technology, Inc. Common" at all 137 settlements, on a single market class (NNM) throughout. Against the share count in our fundamentals file — 247,872,518 shares outstanding dated April 21, 2026 — the latest borrow is 3.99%. Seventh, the Congress lens is stated as recorded: none of the combined, House or Senate aggregates carries a row for this name. The June tracked row implies the June 30 close of $86.23 exactly. The company's fundamentals as collected print fiscal 2025 revenue of $6,707,981,000, net income of $373,895,000 and assets of $8,136,309,000 (fiscal year ended December 31, 2025), with 247,872,518 shares outstanding as of April 21, 2026; those figures are reported as collected and are not used in any lens above. Every price statement here is mechanical, a date and a close from our price file. The Zacks report (published October 20, 2026) postdates the 13F snapshot and the short-interest series; its search-list status, one-month return, industry return and consensus estimates are reported as outlet content in The Hype, and no other figure from it is cited.
- Market context sources: Zacks, "Amkor Technology, Inc. (AMKR) is Attracting Investor Attention: Here is What You Should Know", published October 20, 2026 (Amkor on Zacks.com's list of most searched stocks; shares −19.7% over the past month against +0.7% for the Zacks S&P 500 composite; Zacks Electronics - Semiconductors industry −11.7% over the period; current-quarter consensus EPS estimate $0.79, +54.9% year over year, unchanged over the last 30 days; fiscal-year consensus $2.60). Figures we could not confirm were left out; the external items above are reported speech from that outlet, not GetCoattail measurements.
- Amkor is in the GetCoattail stock-page universe: Amkor Technology (AMKR) stock page. Series data: amkr_lens_data.csv · amkr_short_interest_series.csv. Earlier audits: Aptiv · Pfizer.
Past patterns are not a promise of future results. For education only — not investment advice.
This article describes public filings as of the dates stated. It is not investment advice and makes no recommendation. Filings lag reality: 13F positions are as of June 30, 2026, and later trading is not yet public.
Revision history: v1.0 — October 21, 2026: first publication.