| Year | number of papers published | number of core papers published | proportion |
| 2006 | 228 | 35 | 15.35% |
| 2007 | 256 | 20 | 7.81% |
| 2008 | 302 | 18 | 5.96% |
| 2009 | 271 | 18 | 6.64% |
| 2010 | 224 | 16 | 7.14% |
| 2011 | 211 | 14 | 6.64% |
| 2012 | 209 | 14 | 6.70% |
| 2013 | 192 | 15 | 7.81% |
| 2014 | 181 | 20 | 11.05% |
| 2015 | 146 | 14 | 9.59% |
| 2016 | 21 | 5 | 23.81% |
| totally | 2241 | 189 | 8.43% |