The AMA long ago recognized that the economic principle of supply and demand was vital to its members and to their economic well-being. Early in the 20th century, from 1908 to 1910, the AMA worked with the Carnegie Foundation to have written a so-called "scientific report" under the separate auspices of the Carnegie Foundation. The result was the Flexner Report or Bulletin Number 4 of the Carnegie Commission published in 1910. It called for a drastic reduction in the number of medical schools and doctors in the country and their education along scientific lines. Oddly, this medical report was written not by a doctor but by Abraham Flexner whose only qualifications were as a teacher in Louisville, Kentucky, a basic general education B.A. from Johns Hopkins, and most importantly, his being the brother of Simon Flexner, perhaps the leading physician in the U.S. and head of the Rockefeller Medical Institute. In fact, although Abraham Flexner is attributed as the "author" of this report and although he may have written its words, the ideas that the report is based on came from brother Simon and the AMA.

The Flexner Report still exerts tremendous influence on today's medical education and on the U.S. healthcare system:

No medical school can be created without the permission of the state government. Likewise, the size of existing medical schools is subject to state regulation; Each state branch of the American Medical Association has oversight over the conventional medical schools located within the state; Medicine in the USA and Canada becomes a highly paid and well-respected profession; ... Kessel (1958) argued that the Flexner Report in effect began the cartelization of the American medical profession, a cartelization enforced by the American Medical Association and backed by the police power of each American state. This de facto cartel restricted the supply of physicians, and raised the incomes of the remaining practitioners.

SOURCES: http://en.wikipedia.org/...

Kessel, Reuben, 1958. "Price Discrimination in Medicine", Journal of Law and Economics 1 (Oct., 1958): 20–53.

Slate notes that the physician shortage could reach 100,000 over the next twenty years and also notes the concerns of the Obama administration on the shortage of doctors to provide care especially if reforms are enacted. Interestingly, the same article shows the continuing powerful role the medical community has played in keeping its numbers in line:

Ironically, just a little more than a decade ago, there was a doctor surplus. In 1996, a committee of the Institute of Medicine warned that the United States had a surfeit of doctors caused by foreign-trained physicians coming here to work and recommended freezing med-school class sizes and limiting first-year residency positions. A year later, Slate ran an article on an alternative strategy for reducing the number of doctors approved by the federal Health Care Financing Administration. Under the Graduate Medical Education Demonstration Project, 41 teaching hospitals received $400 million in exchange for not training between 20 percent and 25 percent of the medical residents they would otherwise have trained over the next six years.

SOURCE: http://www.slate.com/...

The United States with over 300,000,000 citizens has only 126 or so medical schools. The United States stopped opening medical schools in the 1980s because of a predicted surplus of doctors, USA Today reported. The same article notes:

The marketplace doesn't determine how many doctors the nation has, as it does for engineers, pilots and other professions. The number of doctors is a political decision, heavily influenced by doctors themselves.

Congress controls the supply of physicians by how much federal funding it provides for medical residencies — the graduate training required of all doctors.

http://www.usatoday.com/...

So, in the medical healthcare equation, bringing about reform of the type of delivery system (whether single payer or something else) is only part of the solution. Another vital part of the equation is increasing the number of health care providers to drive down costs. The reason that the AMA has historically opposed this and indeed, the reason they underwrote the Flexner Report, even choosing in the background its author and making sure of his brother's good standing with their organization, and then propigated its findings, was to artificially limit the number of doctors being produced so as to increase the pay of the medical community. The Obama Administration should set out to work with the states to: 1) increase the number of graduates from state medical schools; 2) set up new, high quality medical schools to supplement the few medical training schools the country has. There exists, after all, a huge pool of highly educated and trained people who wish to work in medicine but are kept out by their "union" (the AMA) with the help of states and our national government. This has historical precedent. After "Sputnik" the US government dramatically increased funding and training for scientists and engineers with a resulting huge increase in their number. The same thing should be done today in medical care: we need more doctors, nurses, and perhaps even a new category(ies) of health care providers with two or three years of medical training and emphasis on primary care.