I used to share a job with another pediatrician, we each worked two days per week. We shared our nanny too, so she landed up with a full time job between the two of us! Technically it was not a job share as we were part of a large group. We did share our call, we each rounded and took call on our usual work days. Loved it. I think a reduced call burden is not so common though, but I was grateful to have it then...
Good luck! If your group were to advertise for a part timer, I bet there would be quite a response...
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kpzr