Competition Research BriefsAR-RB-2026-05

The Federal Merger Review Pipeline, 2016-2025

Notification volume swung widely while annual Second Request rates stayed between 1.6% and 3.0%

By Antitrust Radar Research TeamResearch briefJul 20, 2026Version 1.0 · Current edition

Central finding

Across FY2016-FY2025, the federal HSR program recorded 22,235 reported transactions, 44,014 filings, and 21,496 adjusted transactions.

HSR transactions are notifications reported under the federal premerger program, not a census of every U.S. merger. A reported transaction can involve multiple filings, and the adjusted denominator removes matters for which the agencies could not issue a Second Request. Second Requests and public enforcement actions are different stages with different timing rules. Their counts must not be treated as a finding that every reviewed or reported transaction was anticompetitive. The FY2025 transaction-size table describes adjusted reported transactions in one fiscal year. Differences across value bands are descriptive pipeline counts, not causal estimates, findings of harm, or evidence about transactions outside the HSR reporting universe.

1
source: 10
fiscal years: 41
Second Requests

Publication accountability

External review: No external review registered for version 1.0
Recorded source access / review: 2026-07-18. This is not an independent review date.
Authorship and responsibility: Antitrust Radar Research Team. Publication custody and revision record.

Evidence overview

Procedural evidence route

Follow the finding from notification to bounded review evidence.

The route preserves ten annual tables, 120 fiscal-month records, the separate FY2025 size field, and the boundary between federal procedure and competitive outcome.

Open JSON Run notebook

Declared analytical scope

Notification to adjusted review denominator to public procedural record

No competitive harm, enforcement success, or causal node is asserted. Later outcomes require separate market and counterfactual evidence.

Read boundary

Sources, citations, and policy proposals

Public action docket

What government can require next

4 asks

ForFTC, DOJ, Congress, state attorneys general, and competition researchers

01
Publish stable transaction identifiers
Create durable public identifiers that connect HSR notification, clearance, Second Request, public challenge, remedy, abandonment, and later outcome records without disclosing confidential filing content.
02
Release reusable procedural tables
Publish documented industry, transaction-value, transaction-type, agency, timing, and procedural-stage tables with machine-readable suppression and revision rules.
03
Study the wider acquisition universe
Fund transparent measurement of exempt, below-threshold, serial, and otherwise unreported acquisitions so HSR activity is not mistaken for a census of U.S. mergers.

Evidence still needed

Stable public transaction and proceeding identifiersIndustry, value, type, agency, timing, and stage fieldsBelow-threshold and serial-acquisition research

Open advocacy brief

Reader packet

Reusable

Canonical citation

Antitrust Radar Research Team. (2026, July 20). The Federal Merger Review Pipeline, 2016-2025: Notification volume swung widely while annual Second Request rates stayed between 1.6% and 3.0%. Competition Research Briefs, AR-RB-2026-05 (Version 1.0). Antitrust Radar. https://antitrustradar.org/reports/federal-merger-review-2016-2025

JSON CSV

BibTeX RIS

Briefing packetcite, audit, act Annual pipeline JSON10 exact fiscal-year rows Annual pipeline CSVtransactions and review denominators Executable notebook137 rows / 6 reconciliation checks Monthly field120 exact fiscal-month rows HSR source dossiercustody, method, report Merger observatoryinteractive pipeline histories Action briefpublic research asks Methodologylimits and caveats

Source basis

Federal Trade Commission and U.S. Department of Justice 48th Hart-Scott-Rodino Annual Report, including FY2016-FY2025 annual and fiscal-month tables and the FY2025 transaction-size table.

Source record

Fiscal years

agency report

Source types

Evidence asks

Read the briefing

Evidence index

Claim to public action

Published Jul 20, 2026 · sources through Jul 18, 2026 · version 1.0 · Current edition

Read / Briefing claim

Start with the authored claim and its analytical boundary.

Start with the annual pipeline, monthly field, and procedural outcome boundary.

Interpretation boundaryRead the finding with the report's declared market, geography, vintage, and limitations.

Read the analysis

Competition Research Brief / AR-RB-2026-05

A volatile notification pipeline, with review rates kept in scale

Ten annual records establish the volume arc. Monthly and transaction-size tables show where the latest fiscal year sits inside that federal reporting system.

Reported transactions: 22,235; FY2016-FY2025
Volume range: 1,637 to 3,520; FY2020 / FY2021
Second Request rate: 1.6% to 3.0%; 2.4% across adjusted transactions
Exact source rows: 137; 10 annual / 120 monthly / 7 size bands

01 / Latest volume2,006

FY2025 reported transactions, -1.2% from FY2024.

02 / Latest review41 / 2.1%

Second Requests among adjusted transactions, -0.9 pp from the prior fiscal year.

03 / Size cross-section618 at $1B+

31.8% of the FY2025 adjusted table, carrying 20 Second Requests.

04 / InterpretationPipeline is not outcome

Notification, clearance, Second Request, challenge, remedy, and competitive effect remain distinct stages.

Annual pipeline

Volume swung sharply; the review-rate denominator stayed explicit

FY2016-FY2025 / no smoothing or composite index

Federal premerger pipeline

Notification volume and in-depth review move on separate scales

Fiscal years / reported transactions / adjusted denominator

Reported transactions Second Request rateThe lower panel uses adjusted transactions, not reported transactions, as its denominator.

Ten-year total22,235 transactions

44,014 filings received and 21,496 adjusted transactions.

In-depth review509 Second Requests

2.4% of the pooled adjusted denominator; annual rates are reported separately.

Latest public actions18 actions

The source reports public enforcement actions separately from the 41 FY2025 Second Requests.

Fiscal-month field

The annual total contains a visibly uneven monthly path

120 exact rows

Reported HSR transactions by fiscal month and fiscal year
Fiscal year	Oct	Nov	Dec	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Annual
FY2016	168	243	157	117	127	125	129	168	150	140	166	142	1,832
FY2017	163	215	148	153	153	146	150	209	191	146	219	159	2,052
FY2018	174	207	160	170	141	178	140	222	177	180	223	139	2,111
FY2019	211	254	157	150	145	156	163	191	161	170	173	158	2,089
FY2020	151	206	164	154	138	136	72	57	117	110	170	162	1,637
FY2021	202	400	204	210	278	322	261	299	299	329	353	363	3,520
FY2022	432	575	279	233	206	221	218	211	202	184	197	194	3,152
FY2023	172	207	170	139	150	122	114	139	145	146	162	139	1,805
FY2024	146	208	154	163	139	123	159	175	160	200	203	201	2,031
FY2025	184	225	172	177	213	75	106	140	141	181	191	201	2,006

FY2025 highNovember / 225

Reported transactions in fiscal-month order.

FY2025 lowMarch / 75

A 150-transaction within-year range.

Reading ruleDo not assign cause from timing alone

Calendar, rule, economic, and filing behavior require separate evidence.

FY2025 size field

Transaction value organizes the latest adjusted pipeline

7 exact bands

Transaction valueAdjusted transactionsClearanceSecond Requests

$100M-$150M61 3.1%7 11.5%0 0.0%

$150M-$200M286 14.7%13 4.5%4 1.4%

$200M-$300M195 10.0%7 3.6%0 0.0%

$300M-$500M236 12.1%24 10.2%5 2.1%

$500M-$1B548 28.2%43 7.8%12 2.2%

$1B-$10B599 30.8%85 14.2%16 2.7%

Over $10B19 1.0%10 52.6%4 21.1%

Adjusted table1,944

Exact FY2025 denominator, reconciling to the annual adjusted total.

Under $1 billion: 1,326 / 68.1%
Second Request rate: 1.6%
$1 billion or more: 618 / 31.8%
Second Request rate: 3.2%

The difference between these size groups is descriptive. It does not estimate the effect of transaction value on review or competitive harm.

Exact annual ledger

Every headline remains auditable against its denominator

Open JSON

Annual HSR transactions, filings, adjusted transactions, and Second Requests
Fiscal year	Reported transactions	Filings received	Adjusted transactions	FTC requests	DOJ requests	Total requests	Request rate
FY2016	1,832	3,674	1,772	25	29	54	3.0%
FY2017	2,052	4,083	1,992	33	18	51	2.6%
FY2018	2,111	4,188	2,028	26	19	45	2.2%
FY2019	2,089	4,142	2,030	30	31	61	3.0%
FY2020	1,637	3,249	1,580	23	25	48	3.0%
FY2021	3,520	7,002	3,413	43	23	66	1.9%
FY2022	3,152	6,288	3,029	25	22	47	1.6%
FY2023	1,805	3,515	1,735	26	11	37	2.1%
FY2024	2,031	4,022	1,973	30	29	59	3.0%
FY2025	2,006	3,851	1,944	20	21	41	2.1%

Reproduction packet

Rebuild every published panel from exact public rows

137 exact rows / 6 checks

Input registerThree source-custodied API tables

01
Annual pipeline
Fiscal-year volume, filings, adjusted denominators, and review rates
10 rows
JSON CSV
02
Fiscal-month field
Twelve ordered transaction and filing observations per fiscal year
120 rows
JSON CSV
03
FY2025 size field
Adjusted transactions, clearances, and Second Requests by value band
7 rows
JSON CSV

Reconciliation gateSix assertions before interpretation

0110 annual, 120 monthly, and 7 size rows are present.
02Annual scope is unique across FY2016-FY2025 with the adjusted denominator retained.
03Twelve monthly transaction and filing rows reconcile to every annual record.
04FY2025 size bands reconcile to 1,944 adjusted transactions and 41 Second Requests.
05Annual and size-band Second Request rates recompute from declared denominators.
06All 137 rows retain one official source ID and an observatory handoff.

Public research agenda

Evidence needed to move from procedure to competitive outcomes

Four bounded next steps

01
Publish stable transaction identifiers
Connect notifications, clearance, Second Requests, challenges, remedies, abandonments, and later outcomes without exposing confidential filing material.
02
Preserve transaction context
Release reusable industry, transaction-value, transaction-type, agency, timing, and procedural-stage tables with documented suppression rules.
03
Measure the wider merger universe
Pair HSR reporting with transparent research on exempt, below-threshold, serial, and otherwise unreported acquisitions.
04
Evaluate outcomes separately
Study prices, quality, entry, employment, innovation, access, divestiture performance, and remedy durability after defining the relevant market and counterfactual.

Table of contents

1.Executive summary
2.Research map
3.Evidence handoffs
4.Methods and limits
5.Source register
6.Public action memo

Evidence ledger

Executive summary

Across FY2016-FY2025, the federal HSR program recorded 22,235 reported transactions, 44,014 filings, and 21,496 adjusted transactions. Annual reported volume ranged from 1,637 in FY2020 to 3,520 in FY2021. FY2025 recorded 2,006 reported transactions, down 1.2 percent from FY2024. The annual Second Request rate among adjusted transactions ranged from 1.6 percent to 3.0 percent; 509 Second Requests across the ten-year adjusted denominator produce a descriptive pooled rate of 2.4 percent. FY2025 recorded 41 Second Requests, or 2.1 percent, down 0.9 percentage point from FY2024. Its transaction-size table covers all 1,944 adjusted transactions: 618, or 31.8 percent, were valued at $1 billion or more and accounted for 20 Second Requests. The corresponding 3.2 percent rate and the 1.6 percent rate below $1 billion are descriptive pipeline shares, not causal estimates. Monthly timing, clearance, Second Requests, public enforcement actions, remedies, abandonments, and later competitive outcomes remain distinct. HSR records do not cover every U.S. merger and do not by themselves show whether a reported transaction harmed competition.

22,235

reported HSR transactions

Annual volume ranges from 1,637 in FY2020 to 3,520 in FY2021.

Annual HSR pipeline

1.6% to 3.0%

annual Second Request range

509 requests equal 2.4% of the pooled adjusted denominator.

Adjusted review denominator

618

FY2025 transactions at $1B+

31.8% of the adjusted table and 20 Second Requests.

FY2025 transaction-size table

137

exact public source rows

Annual, monthly, and size-band records describe a federal procedure, not findings about competitive harm.

Source-custodied ledger

Research map

What this briefing connects

Annual pipeline
Fiscal-month field
Transaction-size field
Exact annual ledger
Public research agenda
Methodology and limits

Source basis

Federal Trade Commission and U.S. Department of Justice 48th Hart-Scott-Rodino Annual Report, including FY2016-FY2025 annual and fiscal-month tables and the FY2025 transaction-size table.

Bounded federal procedure

HSR records map notification and review; they do not establish competitive effects.

Merger observatory

Inspect annual, monthly, and size evidence

Open route

Fiscal-month ledger

Reuse all 120 exact monthly records

Open route

HSR source dossier

Audit custody, method, and official report

Open route

Methodology and limits matter

Source basis

Federal Trade Commission and U.S. Department of Justice 48th Hart-Scott-Rodino Annual Report, including FY2016-FY2025 annual and fiscal-month tables and the FY2025 transaction-size table.

Source register

1 cited public record

01 / 1

Inspect source

agency report2026

Source 01

48th Hart-Scott-Rodino Annual Report (FY 2025)

Federal Trade Commission and U.S. Department of Justice

Federal Trade Commission and U.S. Department of Justice Antitrust Division, 48th Hart-Scott-Rodino Annual Report, Fiscal Year 2025, July 2026.

Official annual report on the federal premerger notification program including reported transactions filings Second Requests early termination requests and fiscal-year 2025 transaction-size statistics.

Accessed: Jul 18, 2026
Custody: Public federal government report

Research actions

Audit HSR source View methodology Browse merger activity

Public action memoNear-term

What public institutions should do next

Federal merger oversight needs a durable public evidence chain from notification through review, agency action, remedy, abandonment, and later market outcomes while protecting confidential filing material and keeping procedure distinct from competitive effect.

Audience

FTC, DOJ, Congress, state attorneys general, and competition researchers

1Publish stable transaction identifiersCreate durable public identifiers that connect HSR notification, clearance, Second Request, public challenge, remedy, abandonment, and later outcome records without disclosing confidential filing content.

2Release reusable procedural tablesPublish documented industry, transaction-value, transaction-type, agency, timing, and procedural-stage tables with machine-readable suppression and revision rules.

3Study the wider acquisition universeFund transparent measurement of exempt, below-threshold, serial, and otherwise unreported acquisitions so HSR activity is not mistaken for a census of U.S. mergers.

4Evaluate outcomes after defining the marketLink public procedural records to rigorous later evidence on prices, quality, entry, employment, innovation, access, divestiture performance, and remedy durability.

Evidence needed

Stable public transaction and proceeding identifiersIndustry, value, type, agency, timing, and stage fieldsBelow-threshold and serial-acquisition researchChallenge, remedy, abandonment, and clearance outcomesPost-transaction price, quality, entry, employment, and innovation evidence

Connect to advocacy playbooks

Policy claims are framed as public-interest asks, not legal conclusions. Each ask should be read with the report’s source basis and limitations.