Nearly 300 primary care physicians at MGB who petitioned the National Labor Relations Board in November to let them vote to form a chapter of the Doctors Council of the Service Employees International Union. They have cited overwhelming workloads, insufficient pay for the hours they worked, a shortage of office staff, and lack of a voice in decisions made by MGB. The unionizing effort is part of a flurry of labor organizing by attending physicians and doctors in training at several large health systems in Massachusetts and Rhode Island. Just last year, doctors approved, or took steps toward approving, unions at Salem Hospital (which is part of MGB), Cambridge Health Alliance, Beth Israel Deaconess Medical Center, and Brown University Health and Care New England, both in Rhode Island. The mobilizing mirrors a national trend. Between 2014 and 2019, the number of physicians belonging to unions grew by 26%, from 46,689 to 67,673, although they still only represent a small fraction of all doctors, according to Dr. Kevin Schulman, a professor of medicine at Stanford University in California, who has studied the issue. And the trend has only accelerated since then.