Bodenheimer and Grumbach (1998): "organizations that foot the bill for a patient's care have taken the role of managing the patient's care. Payers and insurers no longer simply write checks; they become involved in decisions about how much care a patient receives, what kind, and by which providers."
Demographics in the US have changed over the last two generations (1) because of increased immigration from a wider variety of nations and ethnic groups and (2) because of the increased in the proportion of the elderly.
Cultural values have changed regarding the operation of health care thus changing how health care is delivered. In addition economic realities have changed to a great extend as is reflected in the cost of medical care as measured in per capita spending and in the health care proportion of GDP (gross domestic product.
In 1960 per capita spending was $141 per annum per capita. In 1996 it had risen to $3,706. In 1960 health care's proportion in GDP was 5 percent. In 2010 it had risen to 15.6 percent of GDP.
These changes have driven health care delivery to a system in which entities other than the doctor make decisions about who gets medical attention, how much they get, what kinds they get and through which practitioner.