Breaking out these categories into specific academic or career orientation is something of a guessing game.  It’s not clear, for example, which category physicians fall into.   About 20,000 doctors of medicine graduate every year, making medicine as the overall top choice for a doctoral degree but which specialization is another matter.  If we look at date reflecting recent enrollments for some of the non-medical possibilities and use these basic categories as a guideline a list of the top ten doctorate degrees begins to emerge.

1. Medical Doctors lead the list; an MD is really a different category than the PhDs and other types of “D’s” that populate the academic centers and professional ranks today.  The largest medical school in the nation is operated by the University of Illinois.  One in six physicians in the state of Illinois is a graduate.
2. PhD in Education or EdD in Education are two options for the top degree in the educational field.  The traditional difference between the two degrees has been that the PhD is research oriented while the EdD is granted to education professionals who wish to work in the top ranks of management.  Larger school districts and many large high schools today are led by EdD graduates.
3. PhD in Psychology or PsyD are two doctorates in psychology that are once again differentiated by the academic tradition of the PhD, and the need for a degree for clinical psychologists.  The PsyD was approved in 1973 by the American Psychological Association and has grown in popularity since.  The licensing requirements for a psychology practice vary among states however, so accreditation of the graduate program and acceptability of the degree are important geographic considerations.
4. PhD in Public Health has become an important degree if for no other reason than that healthcare is far and away the largest industry in the nation, and public health is a rapidly growing segment of that industry.  There is also a DrPH degree increasingly sought by people who are interested in working at the policy making level of the field.
5. PhD in Computer Science is a research position, but much of the research being done in computer technology and theory today is occurring at large corporate entities like Intel.  The DCompSci or DCS degree is also heavily theoretical in its academic orientation, but has evolved in other countries as the business alternative for computer theorists working in product and system development.  In this field of study the PhD remains the more popular choice; at Stanford the Computer Science PhD requires a series of increasingly intense steps.
6. PhD in Civil Engineering is a doctorate in the most common engineering field, one that covers a lot of professional ground in terms of the types of employment.  There are seven major disciplines within the field that, while closely related, can lead to divergent career paths.  A PhD in Civil Engineering can work in a consulting position, can teach, or can become an executive in the urban planning field.
7. PhD in Mechanical Engineering can be a pathway to a career in technology today.  Many of the research directors with electronics companies have mechanical engineering degrees; the mechanics of a design issue may have nothing to do with nuts, bolts and structural issues in contemporary industrial labs.  A doctoral program in mechanical engineering has many specialization options in the academic environment.
8. Doctor of Public Administration (DPA) is at the end of the path for the thousands of professionals returning to school from the public sector who enter into an MPA program and choose to seek a more senior management credential.  A DPA is referred to as the “public service doctorate,” offering specialization and career options in many corners of the public sector.  There is also a PhD in Public Administration, primarily a teaching and research degree.
9. PhD in Biochemistry is a catchall that includes graduates in molecular biology, biotechnology and similar degrees that lead to medical and pharmaceutical research.  Biotech is an important industry today and increasingly, there are doctoral programs designed for it.  But the initial specialists in the field were biochemists, who can also cross into industrial professions where chemistry plays an integral role.
10. PhD in Environmental Science is a degree in a multidisciplinary field that has taken on tremendous cultural and economic importance over the past fifty years.  Sustainability has become an important aspect of planning in the public and private sectors.  The multiplicity of physical sciences and earth sciences involved in this academic discipline can be daunting but is also leading many graduates in the field to a diverse range of employment opportunities.