An interesting site by Google entitled "Government requests directed to Google and YouTube" is a map showing lists of the numbers and types of requests for information by government agencies.
Australia, per capita, seems to be very high, but as Google notes, a single request might contain multiple matters, so other countries may seem much lower.
Of course, even this data may not be complete, since under some Australian legislation it can be an offence to disclose even the fact that a person has been given a notice to produce documents. An example of this is the Commonwealth of Australia Crimes Act 1914. It is an offence under section 3ZQT to disclose the fact that a notice has been issued under section 3ZQN or 3ZQO. These sections were introduced in the Anti-Terrorism Act (No. 2) 2005 - Schedule 6.