| Year | Rank | No. of countries | Rate & value |
| 2000 | 39 | 90 | 4.6 |
| 2001 | 37 | 91 | 4.9 |
| 2002 | 40 | 102 | 4.6 |
| 2003 | 43 | 133 | 3.5 |
| 2004 | 37 | 145 | 5.7 |
| 2005 | 37 | 158 | 5.3 |
| 2006 | 40 | 163 | 4.7 |
| 2007 | 53 | 179 | 5.1 |
| 2008 | 47 | 180 | 5.0 |
| 2009 | 49 | 180 | 4.7 |
| 2010 | 50 | 185 | - |
| 2011 | 36 | 183 | 4.5 |
| 2012 | 58 | 76 | 4.8 |
| 2013 | 66 | 175 | - |
| 2014 | 55 | 175 |
|
| 2015 | 45 | - | 5.3 |