Primary care services improve healthcare outcomes and limit unnecessary specialty care. Thus, it is essential to monitor primary care physician demand and supply projections to suggest evidence-based healthcare reforms and promote better healthcare delivery. This study evaluates 28 demand variables, 50 supply variables, and 26 additional variables associated with the demand and supply projections of physicians by reviewing scenarios from other countries, including Taiwan, Singapore, Japan, and the United States of America. The results indicate that Korea uses less diverse demand and supply indicators and suggest the need to implement variables used in the other four countries to improve projection modeling.