According to their stats, in 2009, 3445 incidences of police misconduct were reported. In 2010, 4861 were reported. That's an increase at the moment, but no data there for 2011 or before 09. I didn't have time to read the report to see if these were broken down into categories such as corruption or brutality, but I will see if any scholarly journal articles have such info. Eventually.
It would be interesting to see the increase since the occupy movement.