| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 3.7 | 74 |
| 2014 | 3.14 | 92 |
| 2013 | 3.49 | 88 |
| 2012 | 2.83 | 103 |
| 2011 | 5.07 | 66 |
| 2010 | 4.27 | 70 |
| 2009 | 0.06 | 172 |
| 2008 | 3.28 | 115 |
| 2007 | 4.69 | 100 |
| 2006 | 4.73 | 88 |
| 2005 | 2.73 | 103 |
| 2004 | 3.51 | 82 |
| 2003 | 2.92 | 77 |
| 2002 | 3.17 | 81 |
| 2001 | 0.6 | 139 |
| 2000 | 4.04 | 68 |
| 1999 | 4.92 | 53 |
| 1998 | 3 | 78 |
| 1997 | 5.14 | 35 |
| 1996 | 5.04 | 28 |
| 1995 | 4.71 | 31 |
| 1994 | 5.83 | 15 |
| 1993 | 7.48 | 11 |
| 1992 | 8.76 | 6 |
| 1991 | 8.14 | 9 |
| 1990 | 5.3 | 12 |
| 1989 | 4.29 | 17 |
| 1988 | 2.04 | 26 |
| 1987 | 1.31 | 40 |
| 1986 | 1.76 | 23 |