At Canadian Immigration Summit 2016 organized by the Conference Board of Canada, IRCC presented some statistics on the Express Entry.
Summary:
151,722 Express Entry profiles were submitted. 54% of profiles submitted were not accepted into the pool because they did not meet minimum entry criteria.
Almost 10,000 Express Entry candidates landed as permanent residents in 2015. As of March 9th, there have been 8451 invitations issued in 6 rounds in 2016. To date, the Department has met the commitment to process 80% of applications within six months.
For more information, you can find an excerpt from the presentation here.