potential value. While defensive medicine is a favored explanation for high medical costs by physicians, Gawande estimated in 2010 it only contributed to 2.4% of the total $2.3 trillion of U.S. health care spending in 2008. Direct-to-consumer advertising Direct-to-consumer advertising can encourage patients to ask for drugs, devices, diagnostics, or procedures. Sometimes service providers will simply give these treatments or services rather than attempting the potentially more unpleasant task of convincing the patient what they have requested is not needed, or is likely to cause more harm than good. Physician predispositions Dartmouth Medical School professor Gilbert Welch argued 2016 that certain predispositions by physicians and the general public may lead to unnecessary health care, including: Attempting to mitigate a risk without considering how small or unlikely the potential benefit is Attempting to fix an underlying problem, instead of using a less-risky monitoring or coping strategy Acting too quickly, when waiting for more information might be wiser Acting without considering the benefits of doing nothing Discounting downsides of diagnostic testing Preferring newer over older treatments without considering the cost of new treatments or the effectiveness of older ones Treating patients with terminal illness to maximize life span over quality of life, without probing a patient's preferences Examples Imaging Overuse of diagnostic imaging, such as X-rays and CT scans, is defined as any application unlikely to improve patient care. Factors that contribute to overuse include "self-referral, patient wishes, inappropriate financially motivated factors, health system factors, industry, media, lack of awareness" and defensive medicine. Respected organizations—such as the American College of Radiology (ACR), Royal College of Radiologists (RCR) and the World Health Organization (WHO)—have developed "appropriateness criteria". The Canadian Association of Radiologists estimated in 2009 that 30% of imaging was unnecessary in the Canadian health care system. 2008 Medicare claims showed overuse with chest CT's. Financial incentives have also been shown to have a significant impact on dental X-ray use with dentists who are paid a separate fee for each X-ray providing more X-rays. Overuse of imaging can lead to a diagnosis of a condition that would have otherwise remained irrelevant (overdiagnosis). Physician self-referral One type of overuse can be physician self-referral. Multiple studies have replicated the finding that when non-radiologists have an ownership interest in the fees generated by radiology equipment—and can self-refer—their use of imaging is unnecessarily higher. The majority of U.S. growth in imaging use (the fastest-growing physician service) comes