| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 8.87 | 117 |
| 2015 | 9.14 | 120 |
| 2014 | 9.27 | 120 |
| 2013 | 7.2 | 97 |
| 2012 | 7.5 | 98 |
| 2011 | 7.9 | 106 |
| 2010 | 8.1 | 99 |
| 2009 | 8.8 | 113 |
| 2008 | 6.4 | 87 |
| 2007 | 6.4 | 81 |
| 2006 | 6.8 | 84 |
| 2005 | 7.18 | 84 |
| 2004 | 8.59 | 107 |
| 2003 | 9.1 | 107 |
| 2002 | 9.6 | 112 |
| 2001 | 10.9 | 128 |
| 2000 | 11.6 | 131 |
| 1999 | 11.6 | 124 |
| 1998 | 11.3 | 126 |
| 1997 | 8.9 | 100 |
| 1996 | 7.6 | 88 |
| 1995 | 5.6 | 61 |
| 1994 | 6.78 | 78 |
| 1993 | 8.19 | 98 |
| 1992 | 7.57 | 93 |
| 1991 | 7.62 | 98 |