| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 81.18 | 36 |
| 2015 | 81.11 | 36 |
| 2014 | 81.03 | 37 |
| 2013 | 81.08 | 39 |
| 2012 | 81.12 | 39 |
| 2011 | 81.16 | 38 |
| 2010 | 81.21 | 37 |
| 2009 | 80.85 | 42 |
| 2008 | 80.5 | 47 |
| 2007 | 80.14 | 52 |
| 2006 | 79.79 | 54 |
| 2005 | 79.46 | 56 |
| 2004 | 79.14 | 58 |
| 2003 | 78.83 | 62 |
| 2002 | 78.54 | 68 |
| 2001 | 78.26 | 71 |
| 2000 | 77.99 | 73 |
| 1999 | 77.7 | 79 |
| 1998 | 77.42 | 81 |
| 1997 | 77.14 | 82 |
| 1996 | 76.84 | 86 |
| 1995 | 77.42 | 85 |
| 1994 | 77.94 | 83 |
| 1993 | 78.4 | 81 |
| 1992 | 78.82 | 82 |
| 1991 | 79.2 | 78 |
| 1990 | 79.56 | 72 |