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 | 4.0000 |
| 1999 | 12.3333 |
| 2000 | 14.8000 |
| 2001 | 22.0000 |
| 2002 | 30.8571 |
| 2003 | 34.4000 |
| 2004 | 46.7500 |
| 2005 | 57.0000 |
| 2006 | 76.5000 |
| 2007 | 86.8947 |
| 2008 | 100.0952 |
| 2009 | 108.7917 |
| 2010 | 126.0000 |
| 2011 | 137.1786 |
| 2012 | 143.7812 |
| 2013 | 162.0909 |
| 2014 | 178.0294 |
| 2015 | 192.6571 |
| 2016 | 212.2857 |
| 2017 | 219.0811 |
| 2018 | 235.7297 |
| 2019 | 252.1892 |
| 2020 | 262.0000 |
| 2021 | 272.8718 |
| 2022 | 277.7073 |
| 2023 | 285.8571 |
| 2024 | 300.2143 |
| 2025 | 296.7907 |
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.