Employment in a key sector of western Pennsylvania's economy has stalled as reimbursement for medical care has fallen and fewer people were admitted to the hospital for treatment. The number of full-time-equivalent health system employees for the three months ending Sept. 30 decreased 2.5 percent or 1,735 people when compared to the same period a year ago, according to a new report by Hospital Council of Western Pennsylvania, a Warrendale-based trade group. During the same period, salary costs decreased $7 million while fringe benefit costs were down $3 million. The decline comes as health system reimbursement is under stress by Medicare and other payors.