What is the difference between UX Design and Service Design?

This question, like other "What's the difference?" questions on this site, is pretty broad and shows a lack of understanding. However, I hope we'll entertain it because defining these emerging fields is helpful to members of this site.

My guess is that UX Design focuses on on-screen user experiences, whereas Service Design encompasses both on-screen and off-screen user experiences, i.e., in person and on the phone as well as on the screen of a device. I'd also venture to guess that Service Design involves People Management and Operations Management more heavily than UX.

The similarities would probably include that both are human-centered problem-solving disciplines, and that both work with UI touchpoints.