A quarter of all public company deals may involve some kind of insider trading, according to the study by two professors at the Stern School of Business at New York University and one professor from McGill University. The study, perhaps the most detailed and exhaustive of its kind, examined hundreds of transactions from 1996 through the end of 2012.

The professors examined stock option movements — when an investor buys an option to acquire a stock in the future at a set price — as a way of determining whether unusual activity took place in the 30 days before a deal’s announcement.

The results are persuasive and disturbing, suggesting that law enforcement is woefully behind — or perhaps is so overwhelmed that it simply looks for the most egregious examples of insider trading, or for prominent targets who can attract headlines.