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The is a database of author affiliation information collated from research articles published in an independently selected group of 82 high-quality science journals. The database is compiled by . The Nature Index provides a close to real-time proxy of high-quality research output and collaboration at the institutional, national and regional level.

The Nature Index is updated monthly, and a 12-month rolling window of data is openly available at  under a Creative Commons non-commercial license. The Nature Index also releases annual tables of country- and institution-level calendar-year output back to 2015, as well as an archive of the annual tables released in previous years.

Article output is counted in two ways:

1. Article count (AC): where a count of one is assigned to an institution or country if one or more authors of the research article are from that institution or country, regardless of how many co-authors there are from outside that institution or country.
2. Fractional count (FC): that takes into account the percentage of authors from that institution (or country) and the number of affiliated institutions per article. For calculation of the FC, all authors are considered to have contributed equally to the article. The maximum combined FC for any article is 1.0.

The ratio of AC to FC gives an indication of the degree to which an institution or country collaborates in its research. Broadly speaking, if the AC is a lot higher than the FC it indicates a high degree of external collaboration and dependency on external resources. If the AC is close in value to the FC it indicates limited collaboration with external researchers and a strong dependency on internal resources.