A doctor friend was telling me the other day that he doesn't know of an instance, in contrast to the nurses' unions.

The UK. https://en.wikipedia.org/wiki/British_Medical_Association

Here's them going on strike the other year: https://www.theguardian.com/society/2016/aug/31/bma-announce...

This made national news a while ago: https://www.nytimes.com/2016/01/10/business/doctors-unionize...

(written before their contract was ratified)

They have a professional association which performs some of the same responsibilities as a union, but its not 1:1

Many employed doctors are in a union in Germany.

medical practices seem to classify hired physicians as contractors, not employees

Controlling supply is the important piece, not being in a union. Once you limit the supply and limit your competition, you don't need a "union". They make up the leadership of the organizations that setup funding for the residency positions, which control how many doctors can be trained every year, effectively controlling the supply of doctors. No one, other than doctors, is incentivized to keep this supply constrained, which I assume is due to lobbying by doctors.

>Medicare-supported training slots are frozen where they existed almost two decades ago, perpetuating inequities in the geographic distribution of training slots and ignoring changes in the geography and demography of the U.S. population

https://www.ncbi.nlm.nih.gov/books/NBK248024/

https://www.aamc.org/advocacy/gme/71178/gme_gme0012.html

http://www.nrmp.org/board-of-directors/

https://en.wikipedia.org/wiki/National_Resident_Matching_Pro...

Residents, interns and fellows are unionized in some states: https://en.wikipedia.org/wiki/Committee_of_Interns_%26_Resid...

Doctors that work for the VA are unionized...as are generally doctors that work for the CA state prison and mental hospital systems.

Sweden - https://slf.se/om-oss/ Denmark - https://www.laeger.dk/english Norway - http://legeforeningen.no/english/