A professor is an accomplished and recognized academic. In most Commonwealth nations, as well as northern Europe, the title "professor" is the highest academic rank at a university. In the United States and Canada, the title of "professor" is also the highest rank, but a higher percentage achieve it. In these areas, professors are scholars with doctorate degrees (typically Ph.D. degrees) or equivalent qualifications. Most professors teach in four-year colleges and universities. An emeritus professor is a title given to selected retired professors with whom the university wishes to continue to be associated due to their stature and ongoing research. Emeritus professors do not receive a salary. However, they are often given office or lab space, and use of libraries, labs, and so on.