| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2015 | 10.36 | 20 |
| 2014 | 9.32 | 25 |
| 2013 | 19.67 | 9 |
| 2012 | 26.53 | 10 |
| 2011 | 11.37 | 25 |
| 2010 | 3.01 | 100 |
| 2009 | -.08 | 176 |
| 2008 | 8.62 | 46 |
| 2007 | 4.15 | 111 |
| 2006 | 5.08 | 81 |
| 2005 | 37.17 | 2 |
| 2004 | 22.04 | 3 |
| 2003 | 6.52 | 33 |
| 2002 | 5.08 | 44 |
| 2001 | 5.92 | 33 |
| 2000 | 3.1 | 90 |
| 1999 | 1.08 | 120 |
| 1998 | 0.01 | 167 |
| 1997 | -.24 | 172 |
| 1996 | -.03 | 168 |
| 1995 | 0.49 | 125 |
| 1994 | 0.16 | 133 |
| 1993 | 1.29 | 69 |
| 1992 | 0.52 | 86 |
| 1991 | 0.16 | 115 |
| 1990 | 0.66 | 83 |
| 1989 | 0.35 | 88 |
| 1988 | 0.2 | 96 |
| 1987 | 0.18 | 93 |
| 1986 | 0.56 | 61 |