Overview and Sampling

The data are based on a sample of 1993 Forms 990, Return of Organization Exempt from Income Tax, and Forms 990-EZ, Short Form Return of Organization Exempt from Income Tax. Organizations used the 1993 forms when their accounting periods ended during the time period December 31, 1993, through November 30, 1994. The sample did not include private foundations, which were required to file on a separate return form. Most churches and other religious organizations were also excluded from the sample because they were not required to file a Form 990 or a Form 990-EZ. However, some of these organizations filed returns voluntarily. The sample included only those returns with receipts of more than $25,000, the filing threshold.

The sample design was split into two parts: the first part included returns of organizations exempt under section 501(c)(3), and the second part included organizations exempt under sections 501(c)(4) through (9). Returns of organizations exempt under other sections were not included in the study. Each part of the sample was classified into strata based on size of total assets, with each stratum sampled at a different rate. For section 501(c)(3) organizations, a sample of 11,882 returns was selected from a population of 167,765. Sampling rates ranged from 0.7 percent for small asset classes to 100 percent for organizations with assets of $10,000,000 or more. For organizations filing under sections 501(c)(4) through (9), a sample of 8,146 returns was selected from a population of 102,841. Sampling rates ranged from 1.9 percent for the small asset classes to 100 percent for organizations with assets of $10,000,000 or more.

The populations for these organizations included some returns of terminated organizations, returns of inactive organizations, duplicate returns, and returns of organizations filed prior to 1993. These returns were not included in the samples, nor in the estimated population counts. For a small number of large organizations whose returns for the 1993 Reporting Year were unavailable for the statistics, data were estimated using prior-year returns.

The data were obtained from returns as originally filed with the Internal Revenue Service. They were subjected to comprehensive testing and correction procedures in order to improve statistical reliability and validity. However, in most cases, changes made to the original return as a result of either administrative processing or taxpayer amendment were not incorporated into the data base.