How Common Is Insider Trading? What Data Shows

The short version

No public dataset can measure exactly how common illegal insider trading is. The observable record is narrower: the SEC filed 456 enforcement actions in fiscal 2025, FINRA said it referred more than 450 insider-trading matters in 2023, and Arkolith tracked 116,967 non-superseded open-market insider purchases or sales in the last 365 days as of August 24, 2026.

How common is insider trading?

Illegal insider trading is common enough to remain a standing enforcement and surveillance priority, but not common enough to measure with one clean public rate. The real denominator is hidden. Regulators can see order data, brokerage accounts, communications, and tips that the public cannot see. Public researchers mostly see enforcement cases, legal insider disclosures, and price-event timing.

That distinction is the whole answer. A legal Form 4 filing is not an illegal insider-trading case. An SEC complaint is not the whole universe of suspicious trading. A FINRA referral is not a conviction. Treat each signal as a different layer of evidence.

Signal	What it measures	What it does not measure
SEC enforcement actions	Cases the SEC chose to bring	Every suspicious trade or every illegal trade
DOJ criminal cases	Charged criminal conduct	Civil cases, closed investigations, or uncharged conduct
FINRA referrals	Surveillance patterns sent onward	Final legal outcomes
Form 4 filings	Disclosed insider transactions	Whether a trade used material nonpublic information
Arkolith Form 4 data	Public filing scale and timing	Private access, duty, intent, or communications

What does the enforcement record show?

The SEC FY2025 enforcement results reported 456 enforcement actions for the year ended September 30, 2025, including 303 standalone actions and 69 follow-on administrative proceedings. The same release said those actions covered misconduct including offering frauds, market manipulation, insider trading, issuer disclosure violations, and adviser fiduciary-duty breaches.

That release also says the SEC closed 1,095 investigated matters involving potentially violative conduct. That number matters because it shows why enforcement totals are not prevalence totals. Some investigated matters close. Some are remediated. Some are not pursued. Some conduct may never reach the SEC.

In the abusive-trading section, the SEC said market abuses such as insider trading and manipulation are central to enforcement and listed insider-trading charges against a former biopharma drug-safety executive, a former investor-relations executive and two others, and a former head of equity trading at an investment firm. That is a docket signal, not an estimate that converts into a market-wide percentage.

How many suspicious cases does surveillance find?

FINRA's insider-trading detection program is one of the clearest windows into scale. In the FINRA insider-trading detection program update, officials described using data to connect traders, insiders, and material news events. They also said the Consolidated Audit Trail helps identify potential insider trading more rapidly.

The same FINRA discussion said that in 2023 FINRA referred more than 450 insider-trading cases. A referral is not proof of wrongdoing. It is a surveillance output: a pattern strong enough to send to the SEC, law enforcement, or another enforcement path for review.

For a prevalence question, that makes FINRA referrals useful but bounded. They show that market-wide surveillance produces hundreds of serious leads. They do not tell you how many leads became civil complaints, criminal convictions, settlements, closures, or false positives.

What does public Form 4 data show?

Public Form 4 data shows that legal insider trading disclosure is large and continuous. The SEC Section 16 guidance says officers, directors, and more-than-10% shareholders generally report most transactions involving company equity to the SEC within two business days on Forms 3, 4, or 5.

Arkolith's production database estimated 9,054,637 insider transaction rows and 3,759,250 filing-event rows on August 24, 2026. The same read found 116,967 non-superseded open-market purchase or sale rows in the previous 365 days across 4,526 tickers, with the latest insider transaction date at August 24, 2026 and the latest Form 4 accepted at 14:07:24 UTC.

Those numbers make Form 4 useful for screening and context. They do not make every insider trade suspicious. Most Form 4 rows are lawful disclosures, compensation mechanics, option exercises, tax withholding, gifts, grants, or ordinary purchases and sales that need context before interpretation.

Illustration: blank filing cards beside a brass evidence tray on dark paper

Why is the true illegal rate hard to know?

The true illegal rate is hard to know because the decisive facts are usually private. Rule 10b5-1 connects insider-trading liability to trading on the basis of material nonpublic information in breach of a duty of trust or confidence. That means a public analyst needs facts about information access, nonpublic timing, duty, intent, tipping, and communications. A Form 4 does not contain all of that.

The Rule 10b5-1 text also describes planned-trading defenses. A planned trade can be lawful even when it looks well timed from the outside. A suspicious-looking trade can also be legitimate if the trader had no material nonpublic information, no breached duty, or a valid prearranged plan.

That is why public writing should use narrow language. Say a trade was disclosed, a filing was accepted, a transaction code was reported, or a regulator alleged misconduct. Do not say the disclosed trade proves illegal insider trading unless an official complaint, order, plea, verdict, or judgment supports that claim.

What does a serious screen look like?

A serious insider-trading screen starts with a question, not an accusation. It asks whether an open-market purchase or sale happened near a material event, whether the insider had a relevant role, whether the transaction was unusual for that person, whether the Form 4 was timely, and whether a 10b5-1 plan was disclosed.

For a public source packet, keep the evidence mechanical:

Field	Why it matters
Ticker and issuer	Names the security and source universe
Insider name and role	Separates officers, directors, 10% owners, and other filers
Transaction date	Anchors the trade clock
Form 4 accepted time	Anchors the public disclosure clock
Transaction code	Separates purchases, sales, grants, option exercises, gifts, and tax withholding
Shares and price if reported	Sizes the disclosed transaction
10b5-1 indicator	Flags planned-trading context
Event timestamp	Tests whether the trade was before or after public news
Primary source URL	Lets a reviewer inspect the filing

Arkolith's insider activity pages, Form 4 data layer, Form 4 transaction-code guide, how insider trading is detected, and who investigates insider trading are built around that source-packet workflow.

What should investors and analysts avoid?

Avoid turning disclosure into accusation. Legal insider buying and selling is part of the U.S. disclosure system. The phrase "insider trading" can mean lawful trades by corporate insiders or illegal trading on material nonpublic information. Confusing those meanings creates false positives.

Also avoid pretending that enforcement totals equal the size of the problem. The SEC brought hundreds of enforcement actions in fiscal 2025 across many categories. FINRA produced hundreds of insider-trading referrals in 2023. Arkolith tracks millions of public insider transaction rows. Those are three different measurements.

One useful rule: public Form 4 data can tell you what was disclosed and when, but it cannot prove what the insider knew.

For an agent workflow, start with /connect, the quickstart, and the MCP API catalog. For API selection, use insider trading data API. For the legal boundary, read why insider trading is illegal, is insider trading a felony, and how to prevent insider trading.

Frequently asked questions about insider-trading prevalence

Is insider trading common?

Illegal insider trading is common enough to produce recurring SEC cases, DOJ prosecutions, and hundreds of FINRA surveillance referrals, but there is no complete public rate. Legal insider trading disclosure is much larger and should not be counted as illegal conduct.

How many insider-trading cases are there each year?

There is no single annual count that captures every case, referral, investigation, charge, settlement, and conviction. The SEC reports annual enforcement totals across all misconduct categories, while FINRA and DOJ describe different parts of the pipeline.

Are most insider trades illegal?

No. Most publicly visible insider trades are disclosed transactions by officers, directors, or large shareholders. A Form 4 filing is a disclosure record, not proof of illegal insider trading.

Can Form 4 data detect insider trading?

Form 4 data can help screen timing, transaction codes, roles, and disclosure delays. It cannot prove material nonpublic information, duty, communications, or intent by itself.

What is the safest way to write about suspicious insider trades?

Use source-bound language: the trade was disclosed, it occurred before or after a named event, the source says the SEC alleged or DOJ charged, and the remaining private elements are unknown unless an official record proves them.

This article explains public enforcement records, public filings, and data workflows. It is not investment advice, legal advice, tax advice, accounting advice, or an allegation about any person or company.