Application of mathematical and statistical methods to scientific literature (as well as to patents and other information media). This enables to evaluate the size of "scientific production" on the assumption that the essence of scientific activity (research and development, B&R activity) is the production of knowledge that finds its reflection in scientific literature.
In reality, this activity is a much more complicated phenomenon; there are domains where research results are not published, like military research or most of industrial research. The main source of bibliometric data is set of bibliographic databases called Science Citation Index (SCI), Social Science Citation Index (SSCI) and Arts & Humanities Citation Index (A&HCI) maintained by the Institute for Scientific Information (ISI) in Philadelphia, USA. They are administered and updated using precisely formulated criteria. In general, bibliometric analysis use data on numbers and authors of scientific publications and on articles and the citations therein (and in patents) to measure the "output" of countries, to identify national and international networks, and to map the development of new (multi-disciplinary) fields of science and technology, as well as to know the inner logic of science development. OECD currently prepares an international methodological manual that will contain guidelines for creating, applying and interpreting the indices based on bibliometric data. This manual will be published in Frascati Family Manuals series.