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| e-Index (Excess Citations)× | m-Quotient (Hirsch m)× | |
|---|---|---|
| Field | Bibliometrics | Bibliometrics |
| Family | Process / pipeline | Process / pipeline |
| Year of origin≠ | 2009 | 2005 |
| Originator≠ | Chun-Ting Zhang | Jorge E. Hirsch |
| Type≠ | Author-level excess-citation impact index | Career-length-normalized author impact rate |
| Seminal source≠ | Zhang, C.-T. (2009). The e-index, complementing the h-index for excess citations. PLoS ONE, 4(5), e5429. DOI ↗ | Hirsch, J. E. (2005). An index to quantify an individual's scientific research output. Proceedings of the National Academy of Sciences, 102(46), 16569-16572. DOI ↗ |
| Aliases | Zhang e-index, excess citation index, e index | Hirsch m-quotient, m-parameter, h-index per year |
| Related | 3 | 3 |
| Summary≠ | The e-index, proposed by Chun-Ting Zhang in 2009, isolates the citations that the h-index throws away. Inside the h-core of an author's h most-cited papers, the h-index implicitly credits each paper with only h citations and discards everything above that, even though top papers may have far more. The e-index recovers exactly this surplus: it is the square root of the difference between the total citations of the h-core and the h-squared citations that the h-index already accounts for. Zhang designed it as a complement rather than a replacement for the h-index, so that the pair (h, e) together describe both the size of an author's productive core and the concentration of excess impact within it. | The m-quotient, defined by Jorge Hirsch in the same 2005 paper that introduced the h-index, normalizes an author's h-index by the length of their scientific career. Because the h-index can only grow over time and never decreases, raw h-values systematically favor senior researchers and make it unfair to compare early-career scientists with established ones. The m-quotient divides the h-index by the number of years since the researcher's first publication, yielding a rate of impact accumulation per year. Hirsch proposed rough benchmarks on this scale, suggesting that a sustained value near 1 characterizes a successful scientist, near 2 an outstanding one, and near 3 a truly exceptional figure, making the m-quotient a tool for comparing researchers at different career stages. |
| ScholarGateDataset ↗ |
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