Do corporate insider buys predict stock returns? What the research says

When a CEO buys their own company's stock on the open market, is that a signal worth trading on? Decades of academic research say yes — with important caveats. Here's the evidence.

· 11 min read · By Insider Option

"Insiders sell for many reasons. They buy for only one." The quote — attributed to Peter Lynch — captures the intuition behind one of the oldest signals in quantitative finance. When a CEO, CFO, or board member buys their own company's stock with their own money, on the open market, it is reasonable to suspect they know something the rest of the market does not.

Whether that suspicion translates into tradeable alpha is one of the most well-studied questions in finance. This post summarizes the evidence.

What is "insider buying"?

In US securities law, a corporate insider is anyone who is (a) an officer or director of a publicly-traded company, or (b) owns more than 10% of its stock. Every time an insider buys or sells shares of their own company, they must file SEC Form 4 within two business days of the trade.

Form 4 filings are public, searchable at SEC EDGAR, and come with standardized fields: the insider's name, their role, the ticker, the transaction type, the share count, the price, and the post-trade holding.

Why buys and sells are not symmetric

Academic research consistently finds that buys are a better signal than sells. The reason is information asymmetry about motivation.

An insider sells for many reasons that have nothing to do with negative information: diversification (they hold concentrated equity compensation and want to reduce single-stock exposure), tax planning, mortgage payment, divorce, estate planning, or an automated 10b5-1 trading plan. Conversely, an insider buys for essentially one reason: they think the stock is likely to go up.

The academic evidence

Lakonishok & Lee (2001)

This landmark paper studied insider trades from 1975 to 1995 and found that heavy insider-buying months were followed by significant outperformance over the subsequent 12 months — roughly 6% annualized excess return for small-cap stocks. The paper established the now-standard "insider buying cluster" as a signal.

Cohen, Malloy & Pomorski (2012)

Extended the analysis and introduced an important refinement: not all insiders are equal. Trades by "opportunistic" insiders (those who trade sporadically and in large amounts) predicted future returns much better than trades by "routine" insiders (those who trade on a regular calendar).

More recent replications

Follow-up studies in the 2010s and 2020s have replicated the core result: insider buying — particularly opportunistic, cluster buying, at small to mid-cap companies — is associated with positive abnormal returns over the subsequent 6 to 12 months. The magnitude has shrunk since Lakonishok & Lee (as expected for any published anomaly), but has not vanished.

What makes the signal stronger

What weakens or breaks the signal

How Insider Option uses this

Our "Insiders Buy" strategy filters Form 4 filings for opportunistic open- market purchases, aggregates by company, and ranks the signal by (a) cluster size, (b) dollar amount relative to the insider's role, and (c) market cap. Holdings are rebalanced on a monthly cadence; the holding period averages six months.

Our published figure for this strategy is measured from the disclosed transaction price to the latest price we hold — so it reflects what the insiders' own positions did, not what a follower entering after the Form 4 appeared would have captured. Because Form 4 is due within two business days, that gap is far smaller here than for Congressional filings, but it is not zero. The current numbers, the filter logic, and the full list of limitations are on our methodology page.

What this is not

Further reading

Informational only. Past performance is not indicative of future returns. See disclaimer.

Frequently asked questions

Does insider buying predict stock returns?
Research including Lakonishok and Lee (2001) and Jeng, Metrick and Zeckhauser (2003) found that open-market insider purchases were associated with positive abnormal returns, concentrated in smaller companies. The effect is weaker for large caps and may have decayed since two-business-day reporting began in 2003.
What is insider cluster buying?
When several unaffiliated insiders at the same company buy shares within a short window, typically a few weeks. Cluster buying is consistently the strongest version of the insider-purchase signal in academic research, because it is harder to explain as an individual's idiosyncratic decision.
Which insider purchases carry the most information?
Open-market purchases (transaction code P) that are not part of a pre-scheduled 10b5-1 plan, are large relative to the insider's own compensation, meaningfully increase their existing holdings, come from a CFO or CEO, and occur alongside other insiders buying.

Keep reading