| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.9 | 83 |
| 2015 | 5.98 | 99 |
| 2014 | 7.03 | 105 |
| 2013 | 6.75 | 112 |
| 2012 | 7.35 | 99 |
| 2011 | 7.97 | 101 |
| 2010 | 10.13 | 98 |
| 2009 | 3.21 | 129 |
| 2008 | 17 | 67 |
| 2007 | 18.23 | 83 |
| 2006 | 15.06 | 101 |
| 2005 | 8.5 | 128 |
| 2004 | 11.42 | 95 |
| 2003 | 12.76 | 84 |
| 2002 | 7.04 | 111 |
| 2001 | 10.93 | 97 |
| 2000 | 3.74 | 132 |
| 1999 | 11.7 | 95 |
| 1998 | 8.43 | 96 |
| 1997 | 7.31 | 121 |
| 1996 | 10.65 | 97 |
| 1995 | 8.52 | 108 |
| 1994 | 9.96 | 107 |
| 1993 | 5.73 | 109 |
| 1992 | 7.38 | 96 |
| 1991 | 1.18 | 118 |
| 1990 | 12.76 | 69 |
| 1989 | 31.02 | 31 |
| 1988 | 17.91 | 61 |
| 1987 | 16.03 | 64 |
| 1986 | 9.56 | 80 |