| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 0.97 | 73 |
| 2015 | 0.71 | 114 |
| 2014 | 1.27 | 113 |
| 2013 | 1.3 | 138 |
| 2012 | 2.19 | 141 |
| 2011 | 4.03 | 112 |
| 2010 | 2.94 | 102 |
| 2009 | 2.76 | 95 |
| 2008 | 4.67 | 139 |
| 2007 | 2.53 | 132 |
| 2006 | 2.24 | 141 |
| 2005 | 2.75 | 120 |
| 2004 | 3.59 | 89 |
| 2003 | 3.51 | 83 |
| 2002 | 2.76 | 94 |
| 2001 | 4.07 | 84 |
| 2000 | 2.27 | 113 |
| 1999 | 0.81 | 127 |
| 1998 | 7.51 | 62 |
| 1997 | 4.45 | 93 |
| 1996 | 4.92 | 98 |
| 1995 | 4.48 | 115 |
| 1994 | 6.26 | 99 |
| 1993 | 4.75 | 93 |
| 1992 | 6.31 | 78 |
| 1991 | 9.3 | 70 |
| 1990 | 8.58 | 67 |
| 1989 | 5.7 | 84 |
| 1988 | 7.15 | 69 |
| 1987 | 3.05 | 92 |
| 1986 | 2.75 | 86 |