The share of doctors who belong to unions is rising^[1] quickly at a time when organized labor is losing ground^[2] with other professions. The Conversation U.S. asked Patrick Aguilar^[3], a Washington University in St. Louis pulmonologist and management professor, to explain why the number of physicians joining unions is growing – a trend that appears likely to continue.

How long have there been health care unions?

U.S. nurses...