reflexively respond to receiving positive test results by ordering more tests. Variation in medical practices can result in SID without producing increased quality outcomes. When standardized treatment pathways are unavailable to agents and principals a degree of uncertainty exists resulting in increased requests for unwarranted services. As a result, overutilization of supplies and services may occur without evidence of improved quality. Due to the number of contributing factors for the consumption of healthcare resources, it is difficult to isolate instances of supplier induced demand. However, there are many reasons for SID in healthcare that are important to understand including reimbursement rates, competition, physician incentives and practices. Increased levels and costs of technology, as well as changing practices and the lack of evidence-based medicine or defined standards of care allow more room for supplier induced demand. To further elaborate, take the example of PSA (prostate specific antigen) testing and early stage prostate cancer. Published guidelines have varied over the past few decades enough to cause doubt in a true standard of care. With a number of treatment options including minimal to no healthcare interventions (watchful waiting, active surveillance, surgery, radiation therapy, etc.), patients may be influenced by providers to consume more healthcare than they would have otherwise given the asymmetry of information and marketing of treatment options from hospitals, physicians and industry. Externalities which influence supplier induced demand include direct to consumer marketing and patient susceptibility to marketing to the extent that demand induced supply is now being documented in health economics. New technology and overutilization Physicians are by nature and duty patient advocates, guiding the patient through joint decision making. This in part stems from a large knowledge differential between the two, a term known as asymmetric information, and evidenced by the differential between patients and physicians' interpretation of medical terms, underscoring the need for physicians to cross examine patients to verify whether they understand the terminology used in the clinical encounter. While the physician bears the brunt of the knowledge differential, the patient is also responsible for sharing their entire medical history, concerns, barriers to and preferences for treatment in order for the physician to be an effective advocate for their health . In effect, the patient provides all relevant information to the physician and relies on the physician to make the clinical decisions for them. This relationship requires a great deal of trust on the part of the