| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 23.4 | 28 |
| 2015 | 23.1 | 29 |
| 2014 | 23.6 | 35 |
| 2013 | 27.3 | 30 |
| 2012 | 31.4 | 27 |
| 2011 | 48.8 | 26 |
| 2010 | 47.6 | 26 |
| 2009 | 42.1 | 32 |
| 2008 | 89.1 | 28 |
| 2007 | 42.4 | 33 |
| 2006 | 39.1 | 28 |
| 2005 | 34.6 | 26 |
| 2004 | 33 | 27 |
| 2003 | 25.4 | 31 |
| 2002 | 27 | 28 |
| 2001 | 26 | 35 |
| 2000 | 43 | 28 |
| 1999 | 32.1 | 30 |
| 1998 | 33.8 | 33 |
| 1997 | 30 | 33 |
| 1996 | 22.6 | 29 |
| 1995 | 24.1 | 28 |
| 1994 | 76.5 | 6 |
| 1993 | 56.6 | 9 |
| 1992 | 44.1 | 9 |
| 1991 | 58.7 | 3 |
| 1990 | 63.5 | 7 |
| 1989 | 45.5 | 10 |
| 1988 | 42.8 | 8 |
| 1987 | 39.9 | 13 |
| 1986 | 21.2 | 12 |