Nearly half of U.S. physician groups said they are still deciding whether to participate in the new health insurance exchange products, according to a survey by the Medical Group Management Association. Forty percent of the more than 1,000 medical groups surveyed said they are still weighing their options on whether to participate in the policies offered by insurers on the exchanges. More than 80 percent of those surveyed said they're concerned about the burden of patient collections on their practices and low provider reimbursement rates.