EARLIER this month, the New York State Legislature passed a bill granting nurse practitioners the right to provide primary care without physician oversight. New York joins 16 other states and the District of Columbia in awarding such autonomy. (Most states still require nurse practitioners to work with physicians under a written practice agreement.) The bill’s authors contend that mandatory collaboration with a physician “no longer serves a clinical purpose” and reduces much-needed access to primary care.

Support for such measures has been widespread. Four years ago the Institute of Medicine called for dropping regulations that prevented nurses from practicing “to the full extent of their education and training.” Last year the president of the American Association of Nurse Practitioners argued that the current diversity of health professionals rendered “hierarchical, physician-centric structures unnecessary.”

As a physician, I couldn’t disagree more. Though well intentioned, such proposals underestimate the clinical importance of physicians’ expertise and overestimate the cost-effectiveness of nurse practitioners.

The impetus behind the new law, which will take effect next year, is the dire shortage of primary-care physicians. A big reason for this scarcity is money. Primary care pays the least of all the medical specialties, and interest in it is at a record low among medical students and residents. At the same time, as baby boomers are starting to retire and the Affordable Care Act adds millions to the rolls of the newly insured, the need for primary-care physicians is growing.