Improving and maintaining health depend on the production and delivery of health care. In turn, the production and delivery of health care depend on health systems, and health systems depend on the capacity of the healthcare workforce to function. It follows, then, that healthcare systems with sufficient human resources are critical in producing and delivering health care and, consequently, in reducing poverty and spurring economic growth in poor countries. Health care is defined here as the prevention, treatment, and management of illness, the preservation and promotion of health through the production and delivery of medical goods, services, and information of a diagnostic, preventive, curative, and palliative nature to all those who need them, when and where needed. The organized provision of such services constitutes a healthcare system.