Secondary information services: Mirrors of scholarly communication. Forces and trends

The statistics published each year by U.S. secondary publishers reveal trends in scientific communication, including political, economic, and social factors. For the first time since 1957, the number of documents abstracted and indexed by U.S. secondary services has declined—following thirty-five years of often rapid growth. The author traces the history of abstracting and indexing services in the United States, considers reasons that the coverage of secondary services has stabilized, and discusses why comprehensive coverage of the scholarly literature may no longer be a viable strategy for secondary services to follow in the years ahead.