For hundreds of different types of jobs—such as teacher, lawyer, and nurse—the Occupational Outlook Handbook tells you:
This is a great database for finding information on careers and on what is important about writing skills in a given career.
Search for "writing and practice and (your profession). For example: "writing AND practice AND engineers"
You can also try "skills and (your profession). For example:"Skills AND Programmers" to find out what skills are currently being sought by employers and how the average worker measures up in those skill areas. Writing and communication will be included in most of the articles.
You can use the links and resources on the next tab (Conduct Secondary Research) to discover more about specific professions and the writing requirements expected in each.