| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.6 | 66 |
| 2015 | 5.99 | 74 |
| 2014 | 5.94 | 73 |
| 2013 | 6.17 | 73 |
| 2012 | 6.13 | 71 |
| 2011 | 7.48 | 97 |
| 2010 | 7.14 | 83 |
| 2009 | 7.87 | 97 |
| 2008 | 8.39 | 125 |
| 2007 | 9.11 | 129 |
| 2006 | 10.28 | 134 |
| 2005 | 11.2 | 139 |
| 2004 | 9.9 | 120 |
| 2003 | 9.5 | 115 |
| 2002 | 9.1 | 103 |
| 2001 | 8.1 | 100 |
| 2000 | 6.1 | 65 |
| 1999 | 6.3 | 65 |
| 1998 | 5.5 | 56 |
| 1997 | 4.7 | 47 |
| 1996 | 4.4 | 40 |
| 1995 | 3.62 | 36 |
| 1994 | 7.97 | 92 |
| 1993 | 4.24 | 45 |
| 1992 | 2.8 | 24 |
| 1991 | 2.59 | 25 |