An acknowledgment index is a method for indexing and analyzing acknowledgements in the scientific literature and, thus, quantifies the impact of acknowledgments. Typically, a scholarly article has a section where the authors acknowledge entities such as funding, technical staff, colleagues, etc. that have contributed materials or knowledge or have influenced or inspired their work. Like a citation index it measures influences on scientific work, but in a different sense; it measures institutional and economic influences as well as informal influences of individual people, ideas, and artifacts. Unlike the impact factor, it does not produce a single overall metric, but analyses the components separately. However, the total number of acknowledgements to an acknowledged entity can be measured and so can the number of citations to the papers in which the acknowledgement appears. The ratio of this total number of citations to the total number of papers in which the acknowledge entity appears can be construed as the impact of that acknowledged entity.
The first automated acknowledgement indexing was created in the search engine and digital library, CiteSeer. However, that feature is no longer supported.