Prices for health care services vary significantly among providers, even for common procedures, and it's often difficult for patients to determine their out-of-pocket costs before receiving care. Some consumer advocates, employers, and health plans are pushing for greater reporting of the prices of health care services as a way to encourage consumers to choose low-cost, high-quality providers and to promote competition based on the value of care. In spite of the challenges, price transparency may be spurred by the growing number of health care consumers who are being required to pay a larger share of their medical bills.