| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 35.1 | 22 |
| 2015 | 38.2 | 19 |
| 2014 | 34.2 | 27 |
| 2013 | 35.5 | 23 |
| 2012 | 33.9 | 24 |
| 2011 | 52.9 | 25 |
| 2010 | 36.4 | 31 |
| 2009 | 37.5 | 35 |
| 2008 | 56.9 | 35 |
| 2007 | 42.6 | 32 |
| 2006 | 35.8 | 29 |
| 2005 | 27.9 | 31 |
| 2004 | 25.2 | 36 |
| 2003 | 21 | 36 |
| 2002 | 11.4 | 40 |
| 2001 | 39.1 | 29 |
| 2000 | 65.4 | 21 |
| 1999 | 36.3 | 26 |
| 1998 | 43.4 | 28 |
| 1997 | 61.2 | 16 |
| 1996 | 66.2 | 9 |
| 1995 | 60.7 | 7 |