As the economy begins to improve, employers across the board are finding it more difficult to retain key talent -- employees who are the strongest performers, have high potential or are in critical jobs. That’s among the findings revealed by a survey of primarily U.S.-based mid-level to senior-level rewards professionals, as reported in Retention of Key Talent and the Role of Rewards, a report published in June 2012 by WorldatWork, an association of total rewards professionals.