Using computer graphics to map origin-destination data describing health care delivery systems.

An interactive graphic computer program, called FLOWMAP, is used to examine the referral patterns of cancer patients in western Washington between 1974 and 1978. FLOWMAP allows one to produce several types of maps from origin-destination data easily and inexpensively. Several maps show some of the significant geographic components of the referral of more than 7000 cancer patients among 13 counties over a 5-year period. It is shown that cancer care has become more decentralized during this period. Nine other possible applications of FLOWMAP to issues of concern regarding the delivery of health care are described. Maps produced by FLOWMAP can be expected to cost 1/30 to 1/50 of the cost of comparable manual methods. An Appendix gives some technical detail regarding the use of FLOWMAP and its data requirements.