Not every article in a journal is considered primary research and therefore "citable", this chart shows the ratio of a journal's articles including substantial research (research articles, conference papers and reviews) in three year windows vs. those documents other than research articles, reviews and conference papers.
| Documents | Year | Value |
| Non-citable documents | 1999 | 0 |
| Non-citable documents | 2000 | 1 |
| Non-citable documents | 2001 | 2 |
| Non-citable documents | 2002 | 2 |
| Non-citable documents | 2003 | 5 |
| Non-citable documents | 2004 | 9 |
| Non-citable documents | 2005 | 11 |
| Non-citable documents | 2006 | 10 |
| Non-citable documents | 2007 | 8 |
| Non-citable documents | 2008 | 9 |
| Non-citable documents | 2009 | 9 |
| Non-citable documents | 2010 | 12 |
| Non-citable documents | 2011 | 12 |
| Non-citable documents | 2012 | 9 |
| Non-citable documents | 2013 | 3 |
| Citable documents | 1999 | 21 |
| Citable documents | 2000 | 52 |
| Citable documents | 2001 | 84 |
| Citable documents | 2002 | 91 |
| Citable documents | 2003 | 123 |
| Citable documents | 2004 | 153 |
| Citable documents | 2005 | 183 |
| Citable documents | 2006 | 174 |
| Citable documents | 2007 | 176 |
| Citable documents | 2008 | 168 |
| Citable documents | 2009 | 161 |
| Citable documents | 2010 | 146 |
| Citable documents | 2011 | 137 |
| Citable documents | 2012 | 90 |
| Citable documents | 2013 | 41 |