| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 5.72 | 68 |
| 2015 | 5.57 | 68 |
| 2014 | 5.16 | 59 |
| 2013 | 5.48 | 65 |
| 2012 | 5.46 | 62 |
| 2011 | 6.5 | 73 |
| 2010 | 7.34 | 89 |
| 2009 | 8.3 | 106 |
| 2008 | 6.2 | 83 |
| 2007 | 6 | 74 |
| 2006 | 7.05 | 91 |
| 2005 | 7.12 | 82 |
| 2004 | 7.76 | 91 |
| 2003 | 8.21 | 95 |
| 2002 | 7.88 | 93 |
| 2001 | 8.98 | 105 |
| 2000 | 10.58 | 118 |
| 1999 | 13.04 | 138 |
| 1998 | 13.26 | 144 |
| 1997 | 11.81 | 131 |
| 1996 | 9.66 | 112 |
| 1995 | 9.45 | 114 |
| 1994 | 8.13 | 94 |
| 1993 | 5.88 | 66 |
| 1992 | 5.18 | 58 |
| 1991 | 12.11 | 136 |