| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 15.7 | 165 |
| 2015 | 15.7 | 165 |
| 2014 | 15.8 | 166 |
| 2013 | 15.9 | 164 |
| 2012 | 16 | 163 |
| 2011 | 16.2 | 164 |
| 2010 | 16.5 | 162 |
| 2009 | 16.8 | 161 |
| 2008 | 17 | 161 |
| 2007 | 17.4 | 161 |
| 2006 | 17.9 | 161 |
| 2005 | 18.5 | 159 |
| 2004 | 19.4 | 155 |
| 2003 | 20.4 | 152 |
| 2002 | 21.5 | 147 |
| 2001 | 22.5 | 144 |
| 2000 | 23.5 | 142 |
| 1999 | 24.2 | 141 |
| 1998 | 24.9 | 140 |
| 1997 | 25.5 | 140 |
| 1996 | 26 | 140 |
| 1995 | 26.6 | 140 |
| 1994 | 27 | 138 |
| 1993 | 27.4 | 138 |
| 1992 | 27.7 | 137 |
| 1991 | 27.9 | 138 |
| 1990 | 27.9 | 138 |
| 1989 | 27.9 | 138 |
| 1988 | 27.8 | 140 |
| 1987 | 27.7 | 141 |
| 1986 | 27.4 | 141 |