| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2010 | 11.5 | 67 |
| 2009 | 10.68 | 71 |
| 2008 | 10.89 | 69 |
| 2007 | 19.07 | 50 |
| 2006 | 17.44 | 55 |
| 2005 | 18.81 | 54 |
| 2004 | 19.44 | 54 |
| 2003 | 20.29 | 51 |
| 2002 | 22.01 | 46 |
| 2001 | 24.36 | 39 |
| 2000 | 24.37 | 41 |
| 1999 | 26.19 | 40 |
| 1998 | 26.17 | 43 |
| 1997 | 21.58 | 51 |
| 1996 | 13.33 | 81 |
| 1995 | 17.18 | 65 |
| 1994 | 34.01 | 30 |
| 1993 | 19.44 | 57 |
| 1992 | 10.61 | 87 |
| 1991 | 32.2 | 31 |
| 1990 | 33.33 | 25 |
| 1989 | 28.57 | 35 |
| 1988 | 25.93 | 39 |
| 1987 | 28 | 33 |