Medical manpower is ordinarily expressed as a ratio of the number of physicians (e.g., neurosurgeons) to the population of the geographic area (e.g., country). The many other factors that go into assessing medical manpower needs and the manner in which those factors may vary from one country to another and from one time to another are described. Despite the paucity of physicians in some countries and in some parts of the world, there is a surplus of physicians worldwide.