| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 16.8 | 155 |
| 2015 | 16.8 | 155 |
| 2014 | 17 | 154 |
| 2013 | 17.1 | 153 |
| 2012 | 17.3 | 153 |
| 2011 | 17.5 | 154 |
| 2010 | 17.9 | 151 |
| 2009 | 18.3 | 149 |
| 2008 | 18.8 | 148 |
| 2007 | 19.3 | 148 |
| 2006 | 19.8 | 146 |
| 2005 | 20.2 | 145 |
| 2004 | 20.7 | 146 |
| 2003 | 21.2 | 145 |
| 2002 | 21.6 | 145 |
| 2001 | 22.1 | 146 |
| 2000 | 22.7 | 147 |
| 1999 | 23.2 | 146 |
| 1998 | 23.7 | 145 |
| 1997 | 24.3 | 144 |
| 1996 | 24.7 | 144 |
| 1995 | 25.1 | 143 |
| 1994 | 25.4 | 143 |
| 1993 | 25.6 | 143 |
| 1992 | 25.8 | 143 |
| 1991 | 26 | 143 |
| 1990 | 26.2 | 143 |
| 1989 | 26.4 | 142 |
| 1988 | 26.7 | 143 |
| 1987 | 27 | 143 |
| 1986 | 27.3 | 143 |