Very few--less than 1% over time. We resolve about 98% of the cases, or the complaints get discontinued, and about 1% of the cases have gone to Federal Court over, say, the last 25 years. And we've won most of those.
Evidence of meeting #7 for Access to Information, Privacy and Ethics in the 40th Parliament, 2nd session. (The original version is on Parliament’s site, as are the minutes.) The winning word was requests.
A recording is available from Parliament.