How many lobbyists are really breaking the law?

From National Journal:

A recent study found that a majority of lobbyists may not be fully disclosing their past government work, which would be a violation of the Lobbying Disclosure Act and Honest Leadership and Open Government Act.
The study, co-authored by a James Madison University political science professor, found that, based on the biographies of 1,600 registered lobbyists in 2008, 57 percent didn't disclose their past government work.
But, as Mother Jones reports, the researchers didn't look into all the ways lobbyists can disclose their past work. And that means that some lobbyists who were thought to be in violation may actually have filed their paperwork properly.