| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 5.67 | 98 |
| 2014 | 5.9 | 100 |
| 2013 | 6.61 | 100 |
| 2012 | 5.64 | 102 |
| 2011 | 5.83 | 103 |
| 2010 | 5.79 | 105 |
| 2009 | 6.27 | 105 |
| 2008 | 5.81 | 105 |
| 2007 | 5.47 | 104 |
| 2006 | 5.52 | 109 |
| 2005 | 6.42 | 101 |
| 2004 | 6.7 | 102 |
| 2003 | 6.89 | 104 |
| 2002 | 6.79 | 105 |
| 2001 | 8.78 | 93 |
| 2000 | 8.3 | 99 |
| 1999 | 9.31 | 89 |
| 1998 | 8.88 | 96 |
| 1997 | 7.52 | 101 |
| 1996 | 8.11 | 100 |
| 1995 | 9.45 | 95 |
| 1994 | 8.85 | 92 |
| 1993 | 9.01 | 92 |
| 1992 | 9.88 | 89 |
| 1991 | 8.05 | 95 |
| 1990 | 13.6 | 77 |
| 1989 | 14.11 | 71 |
| 1988 | 15.52 | 68 |
| 1987 | 15.92 | 61 |
| 1986 | 17.43 | 58 |