Collectively, all men and women working in the provision of health services whether as individual practitioners or employees of health institutions and programs; whether or not professionally trained; and whether or not subject to public regulation. Facilities and manpower are the principal health resources used in producing health services. In 1973 there were over four million people working in over 200 health occupations. Some of these are shown in the following table. It is often difficult to agree on which occupations are health occupations, but the table does suggest the variety of possibilities.