Special Information and Insider Trading
Jaffe established the event-study foundation: legal insider transactions contain information, but measured results depend on horizons, benchmarks, and trading frictions.
Jaffe is the starting point for the modern empirical literature on legal insider trading. Using the Official Summary of Security Transactions and Holdings, the paper studies reported transactions by officers, directors, and large shareholders before electronic Form 4 filing existed. Its central contribution is methodological as much as substantive: it treats an insider transaction as an event, builds portfolios around intensive buying or selling, and asks whether the returns differ from an appropriate market benchmark.
Later papers read Jaffe as evidence that legal trades are not pure noise. That conclusion needs its historical setting attached. The Official Summary arrived with delay, spreads were wider, and the sample predates modern factor models, electronic disclosure, and the current two-business-day Form 4 deadline. Equal-weighted designs also give small and less liquid firms substantial influence. Jaffe therefore supports studying reported activity, not copying a transaction or attaching a directional claim to an individual company.
The paper also began a chain of refinements visible across this bibliography: Finnerty revisited market efficiency, Seyhun added transaction costs and firm size, Lakonishok and Lee separated purchases from sales, and Cohen, Malloy, and Pomorski separated routine from opportunistic activity. Insider Atlas uses Jaffe as a historical anchor while presenting the newer qualifications beside the data.
Abstract excerpt
The publisher record notes that the 1974 article did not supply an abstract:
“No abstract is available for this item.”
Connections in Insider Atlas
Compare the paper’s broad event concept with the later, tightly defined BGDE cluster event and its company history. Those pages are descriptive examples of the modern schema, not replications of Jaffe’s sample.