| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 1.4 | 44 |
| 2015 | 0.8 | 50 |
| 2014 | 1.6 | 54 |
| 2013 | 1.6 | 55 |
| 2012 | 2.7 | 50 |
| 2011 | 3 | 50 |
| 2010 | 2.7 | 55 |
| 2009 | 2.4 | 56 |
| 2008 | 3.1 | 56 |
| 2007 | 7.9 | 52 |
| 2006 | 4.7 | 55 |
| 2005 | 2.3 | 56 |
| 2004 | 1.6 | 65 |
| 2003 | 1.7 | 55 |
| 2002 | 1.8 | 51 |
| 2001 | 1.4 | 57 |
| 2000 | 4.2 | 46 |
| 1999 | 4.9 | 46 |
| 1998 | 4.7 | 50 |
| 1997 | 6.6 | 45 |
| 1996 | 6.4 | 35 |
| 1995 | 7.3 | 34 |
| 1994 | 6.9 | 33 |
| 1993 | 4.4 | 37 |