| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 12.8 | 192 |
| 2015 | 12.4 | 192 |
| 2014 | 12.2 | 192 |
| 2013 | 12.2 | 192 |
| 2012 | 12.3 | 192 |
| 2011 | 12.5 | 193 |
| 2010 | 12.7 | 193 |
| 2009 | 13.3 | 192 |
| 2008 | 13.9 | 189 |
| 2007 | 14.8 | 183 |
| 2006 | 15.8 | 176 |
| 2005 | 16.9 | 170 |
| 2004 | 18.1 | 166 |
| 2003 | 19.4 | 158 |
| 2002 | 20.7 | 153 |
| 2001 | 21.9 | 149 |
| 2000 | 22.9 | 145 |
| 1999 | 23.6 | 143 |
| 1998 | 24.2 | 143 |
| 1997 | 24.7 | 142 |
| 1996 | 25.1 | 141 |
| 1995 | 25.5 | 141 |
| 1994 | 25.8 | 141 |
| 1993 | 25.9 | 142 |
| 1992 | 25.8 | 144 |
| 1991 | 25.6 | 145 |
| 1990 | 25.5 | 145 |
| 1989 | 25.2 | 149 |
| 1988 | 24.9 | 152 |
| 1987 | 24.8 | 155 |
| 1986 | 24.5 | 156 |