| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 7.93 | 107 |
| 2015 | 8.22 | 109 |
| 2014 | 8.91 | 113 |
| 2013 | 8.96 | 114 |
| 2012 | 9 | 115 |
| 2011 | 9 | 116 |
| 2010 | 8.9 | 114 |
| 2009 | 8.7 | 112 |
| 2008 | 8.8 | 128 |
| 2007 | 8.6 | 122 |
| 2006 | 6.5 | 74 |
| 2005 | 4.6 | 45 |
| 2004 | 4.7 | 48 |
| 2003 | 8.5 | 101 |
| 2002 | 8.35 | 96 |
| 2001 | 6.13 | 66 |
| 2000 | 7.78 | 95 |
| 1999 | 8.31 | 98 |
| 1998 | 8.86 | 101 |
| 1997 | 6.67 | 74 |
| 1996 | 5.78 | 59 |
| 1995 | 5.4 | 55 |
| 1994 | 5.7 | 62 |
| 1993 | 5.9 | 67 |
| 1992 | 5.4 | 61 |
| 1991 | 5.9 | 71 |