e-index
The e-index (Zhang 2009) is simply a measure of the excess citations in the h-index core beyond those necessary to produce the core itself. It is measured as:
$$e=\sqrt{C^H-h^2}=\sqrt{\sum\limits_{i=1}^{h}{C_i}-h^2}.$$Graphically, it is the square-root of the total citations within the upper part of the citation curve.
History
| Year | e |
|---|---|
| 1997 | 0.0000 |
| 1998 | 2.0000 |
| 1999 | 5.2915 |
| 2000 | 7.0711 |
| 2001 | 9.8489 |
| 2002 | 12.5698 |
| 2003 | 15.5563 |
| 2004 | 20.3224 |
| 2005 | 25.0000 |
| 2006 | 30.9677 |
| 2007 | 35.8050 |
| 2008 | 40.6817 |
| 2009 | 45.0111 |
| 2010 | 50.1597 |
| 2011 | 55.2178 |
| 2012 | 59.6406 |
| 2013 | 65.1383 |
| 2014 | 69.9214 |
| 2015 | 74.2361 |
| 2016 | 78.7020 |
| 2017 | 81.9939 |
| 2018 | 85.6563 |
| 2019 | 89.1628 |
| 2020 | 92.2442 |
| 2021 | 95.4411 |
| 2022 | 98.4175 |
| 2023 | 101.3114 |
| 2024 | 103.9230 |
| 2025 | 104.8427 |
References
- Zhang, C.-T. (2009) The e-index, complementing the h-index for excess citations. PLoS ONE 4(5):e5429.