| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2014 | 14.84 | 100 |
| 2013 | 14.78 | 114 |
| 2012 | 14.85 | 113 |
| 2011 | 17.4 | 95 |
| 2010 | 23.87 | 61 |
| 2009 | 24.29 | 58 |
| 2008 | 23.13 | 67 |
| 2007 | 24.77 | 62 |
| 2006 | 27.38 | 51 |
| 2005 | 28.63 | 44 |
| 2004 | 30.62 | 37 |
| 2003 | 20.37 | 66 |
| 2002 | 21.87 | 57 |
| 2001 | 20.01 | 63 |
| 2000 | 19.18 | 61 |
| 1999 | 23.79 | 45 |
| 1998 | 22.26 | 51 |
| 1997 | 20.04 | 57 |
| 1996 | 20.96 | 50 |
| 1995 | 22.52 | 40 |
| 1994 | 25.87 | 35 |
| 1993 | 23.73 | 40 |
| 1992 | 24.14 | 35 |
| 1991 | 20.48 | 39 |
| 1990 | 19.69 | 44 |
| 1989 | 35.35 | 21 |
| 1988 | 38.65 | 18 |
| 1987 | 40.94 | 15 |
| 1986 | 35.76 | 18 |