Erik Stephens writes:

Does anyone know what kinds of operations fall under 'system'? Task switching, paging, these kinds of things? The computer can execute instruction being part of the operating system (usually priviledged code) or of user processes. The first would be accounted for as system, the latter as user time.

System time includes (as you expect) scheduling, but also memory management (swapping in and out, paging in and out), IO activity, inter-process communication and all other operating system services. Dieter