| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 19.79 | 41 |
| 2015 | 22.16 | 61 |
| 2014 | 24.66 | 56 |
| 2013 | 22.32 | 69 |
| 2012 | 20.92 | 78 |
| 2011 | 20.78 | 78 |
| 2010 | 19.39 | 82 |
| 2009 | 17.66 | 92 |
| 2008 | 21.45 | 72 |
| 2007 | 20.06 | 80 |
| 2006 | 19.27 | 81 |
| 2005 | 19.76 | 77 |
| 2004 | 19.69 | 71 |
| 2003 | 17.69 | 76 |
| 2002 | 19.57 | 68 |
| 2001 | 22.9 | 53 |
| 2000 | 23.56 | 50 |
| 1999 | 18.18 | 64 |
| 1997 | 9.74 | 108 |
| 1996 | 9.31 | 116 |
| 1995 | 10.21 | 103 |
| 1994 | 11.14 | 96 |
| 1993 | 10.78 | 98 |
| 1992 | 10.67 | 90 |
| 1991 | 9.91 | 87 |
| 1990 | 9.77 | 84 |
| 1989 | 9.15 | 85 |
| 1988 | 9.52 | 82 |
| 1987 | 9.23 | 84 |
| 1986 | 8.49 | 89 |