| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 14.4 | 55 |
| 2015 | 15.21 | 94 |
| 2014 | 16.15 | 93 |
| 2013 | 16.39 | 100 |
| 2012 | 17.36 | 97 |
| 2011 | 16.14 | 102 |
| 2010 | 16.52 | 99 |
| 2009 | 17.2 | 94 |
| 2008 | 18.88 | 89 |
| 2007 | 13.94 | 122 |
| 2006 | 12.62 | 127 |
| 2005 | 12.31 | 128 |
| 2004 | 12.56 | 114 |
| 2003 | 11.28 | 121 |
| 2002 | 11.2 | 122 |
| 2001 | 12.03 | 114 |
| 2000 | 11.81 | 108 |
| 1999 | 11.48 | 109 |
| 1998 | 13.96 | 89 |
| 1997 | 10.42 | 104 |
| 1996 | 9.17 | 118 |
| 1995 | 9.08 | 115 |
| 1994 | 8.08 | 113 |
| 1993 | 7.59 | 117 |
| 1992 | 7.28 | 113 |
| 1991 | 7.21 | 112 |
| 1990 | 7.58 | 104 |
| 1989 | 7.58 | 99 |
| 1988 | 7.91 | 93 |
| 1987 | 9.14 | 85 |
| 1986 | 9.08 | 86 |