12.4.3 The rates-under-treatment approach is based on a descriptive enumeration of persons who have utilized the services of the health and welfare agencies of a community. There are several advantages. Data are readily available and they reflect direct information about individuals and an overview of the services being provided. One of the disadvantages is the problem of guaranteeing anonymity and confidentially. Another disadvantage is the influence of the care providers in estimating the needs of a community's population. This approach also excludes information about those who are in need but are seeking or receiving care.