| Ranking | Count | Year | Keywords |
| 1 | 21 | 2011 | china |
| 2 | 12 | 2011 | CO2 emission |
| 3 | 11 | 2015 | adjustment |
| 4 | 10 | 2012 | agriculture |
| 5 | 10 | 2013 | behavior |
| 6 | 10 | 2010 | agreement |
| 7 | 9 | 2012 | agglomeration |
| 8 | 9 | 2012 | business |
| 9 | 7 | 2013 | asia |
| 10 | 7 | 2010 | bilateral trade |