The information presented in this report was obtained from many sources, including federal and state agencies, private research organizations, and professional associations. The data were collected using many research methods, including surveys of a universe (such as all colleges) or of a sample, compilations of administrative records, and statistical projections. Digest users should take particular care when comparing data from different sources. Differences in sampling, data collection procedures, coverage of target population, timing, phrasing of questions, scope of nonresponse, interviewer training, and data processing and coding mean that results from different sources may not be strictly comparable. Following the general discussion of data accuracy below, descriptions of the information sources and data collection methods are presented, grouped by sponsoring organization. More extensive documentation of a particular survey's procedures does not imply more problems with the data, only that more information is available.