| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 28 | 74 |
| 2014 | 25.92 | 92 |
| 2013 | 21.75 | 118 |
| 2012 | 22.51 | 116 |
| 2011 | 22.48 | 120 |
| 2010 | 28.21 | 79 |
| 2009 | 27.72 | 78 |
| 2008 | 28.33 | 84 |
| 2007 | 30.47 | 71 |
| 2006 | 31.12 | 64 |
| 2005 | 31.26 | 60 |
| 2004 | 35.4 | 39 |
| 2003 | 37.45 | 28 |
| 2002 | 39.43 | 24 |
| 2001 | 40.08 | 23 |
| 2000 | 38.85 | 26 |
| 1999 | 29.62 | 68 |
| 1998 | 27.01 | 87 |
| 1997 | 28.67 | 82 |
| 1996 | 31.56 | 59 |
| 1995 | 39.34 | 20 |
| 1994 | 41.01 | 19 |
| 1993 | 46.53 | 10 |
| 1992 | 46.05 | 13 |
| 1991 | 36.94 | 34 |
| 1990 | 37.59 | 31 |
| 1989 | 36.23 | 32 |
| 1988 | 39.24 | 20 |
| 1987 | 42.74 | 15 |
| 1986 | 40.13 | 15 |