| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 0 | 100 |
| 2015 | 0.8 | 111 |
| 2014 | 4.52 | 56 |
| 2013 | 5.22 | 58 |
| 2012 | 4.5 | 79 |
| 2011 | 4.88 | 94 |
| 2010 | 5.66 | 58 |
| 2009 | 7.84 | 32 |
| 2008 | 13.42 | 40 |
| 2007 | 9.36 | 28 |
| 2006 | 11.47 | 20 |
| 2005 | 13.8 | 16 |
| 2004 | 12.32 | 21 |
| 2003 | 9.45 | 38 |
| 2002 | 9.16 | 37 |
| 2001 | 11.23 | 26 |
| 2000 | 10.99 | 31 |
| 1999 | 10.05 | 33 |
| 1998 | 11.67 | 37 |
| 1997 | 13.23 | 37 |
| 1996 | 17.52 | 45 |
| 1995 | 23.19 | 42 |
| 1994 | 13.53 | 67 |
| 1993 | 9.78 | 68 |
| 1992 | 21.79 | 36 |
| 1991 | 28.71 | 29 |
| 1990 | 19.04 | 36 |
| 1989 | 16.51 | 35 |
| 1988 | 20.83 | 29 |
| 1987 | 16.85 | 31 |
| 1986 | 11.84 | 44 |