| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 3.74 | 106 |
| 2015 | 14.16 | 42 |
| 2014 | 17.05 | 22 |
| 2013 | 12.84 | 62 |
| 2012 | 14.39 | 52 |
| 2011 | 19.15 | 34 |
| 2010 | 22.36 | 33 |
| 2009 | 16.46 | 56 |
| 2008 | 15.55 | 76 |
| 2007 | 20.42 | 70 |
| 2006 | 16.97 | 89 |
| 2005 | 9.91 | 115 |
| 2004 | 13.47 | 84 |
| 2003 | 11.79 | 90 |
| 2002 | 9.89 | 93 |
| 2001 | 5.64 | 126 |
| 2000 | 4.91 | 127 |
| 1999 | 6.49 | 129 |
| 1998 | 2.93 | 125 |
| 1997 | 20.19 | 58 |
| 1996 | 25.33 | 43 |
| 1995 | 29 | 41 |
| 1994 | 23.18 | 67 |
| 1993 | 28.03 | 42 |
| 1992 | 39.02 | 27 |
| 1991 | 19.57 | 52 |
| 1990 | 20.06 | 47 |
| 1989 | 12.92 | 80 |
| 1988 | 8.04 | 90 |
| 1987 | 11.13 | 78 |
| 1986 | 32.7 | 17 |