Up until last week Google and other companies were barred for disclosing how many requests they were receiving from the National Security Agency and PRISM. This ban was lifted last week when the US Government settled a lawsuit with the tech industry. Now companies such as Google can list NSA requests in their Transparency Report, a semi-annual publication that shows how often governments collect information on its users.
Google has already published its numbers, which you can see below. This shows how many times the government has obtained not only account information, but actual user content as well like Gmail messages.
Facebook has also published their numbers.
The other companies that are involved in the lawsuit are Yahoo, Microsoft and LinkedIn has also published numbers as well. As you can see from the graphs above the numbers the companies publish are restricted to aggregate ranges, under the terms of the settlement.