The baby boom started in 1947 (or April 1946 if you want to count 9 months from the end of the war) and ran through 1964 with a peak in 1957. Most geriatric specialists will tell you that people 75-84 and older with complex medical conditions are their buisness in addition to those 85 and older. The pool of people in that age group is going to expand over the next 30 years and be a good thing well into the middle of this century. While the mid-levels are delivering primary care to kids and younger adults as well as episodic care for minor injuries and infections, you are going to find that they won't want to touch the "primary care" of elderly people who are more frail or who have three or more chronic medical conditions. In addition, physicians who treat the diseases that are most common in old age (certain cancers, degenerative joint diseases, cardiovascular disease, etc) will see an increase in depand beginning in about 2022, or just about the time you finish your fellowships. (if you are starting medical school in the next year or two).