a-index
The a-index (Jin 2006; Rousseau 2006) is used to describe the citations within the h-index core itself, being simply the average number of citations per core publication, or
$$a=\frac{C^H}{h}=\frac{\sum\limits_{i=1}^{h}{C_i}}{h}.$$The minimum value of a is h (since every one of the h publications must have at least h citations).
History
| Year | a |
|---|---|
| 1997 | 1.0000 |
| 1998 | 4.3333 |
| 1999 | 12.3333 |
| 2000 | 15.0000 |
| 2001 | 22.1667 |
| 2002 | 27.7500 |
| 2003 | 34.2000 |
| 2004 | 46.4167 |
| 2005 | 56.6667 |
| 2006 | 75.9375 |
| 2007 | 86.4737 |
| 2008 | 99.8095 |
| 2009 | 108.4167 |
| 2010 | 125.6400 |
| 2011 | 136.8929 |
| 2012 | 143.1562 |
| 2013 | 161.5758 |
| 2014 | 177.7941 |
| 2015 | 192.4571 |
| 2016 | 211.9714 |
| 2017 | 218.7027 |
| 2018 | 235.2973 |
| 2019 | 251.8649 |
| 2020 | 261.9211 |
| 2021 | 272.5641 |
| 2022 | 277.2439 |
| 2023 | 291.3415 |
| 2024 | 299.1429 |
| 2025 | 293.8182 |
References
- Jin, B. (2006) h-index: An evaluation indicator proposed by scientist. Science Focus 1(1):8–9.
- Rousseau, R. (2006) New developments related to the Hirsch index. Science Focus 1(4):23–25.