Worldwide, non-compliance is a major obstacle to the effective delivery of health care. In 2003, the World Health Organization estimated that only about half the patients with chronic diseases living in developed countries follow treatment recommendations. In particular, low rates of adherence to therapies for asthma, diabetes, and hypertension are thought to contribute substantially to the human and economic burden of those conditions. Compliance rates may be overestimated in the medical literature, as compliance is often high in the setting of a formal clinical trial but drops off in a "real-world" setting.