On the demand versus need for medical services and the concept of "shortage".
D001291:Attitude of Health Personnel; D001294:Attitude to Health; D003256:Community Participation; D003365:Costs and Cost Analysis; D003695:Delivery of Health Care; D004470:Economics, Medical; D008433:Mathematics; D010548:Personal Health Services / Q000600:supply & distribution*; D011153:Population; D014481:United States