| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 5.25 | 101 |
| 2014 | 7.27 | 91 |
| 2013 | 8.76 | 87 |
| 2012 | 9.86 | 74 |
| 2011 | 10.21 | 73 |
| 2010 | 9.97 | 80 |
| 2009 | 12.38 | 63 |
| 2008 | 12.52 | 66 |
| 2007 | 13.23 | 60 |
| 2006 | 14.49 | 61 |
| 2005 | 16.14 | 59 |
| 2004 | 17.3 | 57 |
| 2003 | 17.45 | 55 |
| 2002 | 17.27 | 54 |
| 2001 | 17.65 | 56 |
| 2000 | 18.28 | 56 |
| 1999 | 20.55 | 52 |
| 1998 | 18.03 | 63 |
| 1997 | 15.92 | 72 |
| 1996 | 15.1 | 74 |
| 1995 | 16 | 71 |
| 1994 | 13.56 | 77 |
| 1993 | 34.1 | 28 |
| 1992 | 23.81 | 48 |
| 1991 | 17.43 | 64 |
| 1990 | 20.6 | 56 |
| 1989 | 21.24 | 51 |
| 1988 | 17.42 | 57 |
| 1987 | 12.05 | 74 |
| 1986 | 13.56 | 67 |