| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 18.9 | 140 |
| 2015 | 18.8 | 140 |
| 2014 | 18.8 | 142 |
| 2013 | 18.9 | 143 |
| 2012 | 19 | 144 |
| 2011 | 19 | 145 |
| 2010 | 19 | 146 |
| 2009 | 19.1 | 146 |
| 2008 | 19.2 | 146 |
| 2007 | 19.4 | 146 |
| 2006 | 19.6 | 148 |
| 2005 | 19.8 | 150 |
| 2004 | 20 | 151 |
| 2003 | 20.2 | 154 |
| 2002 | 20.4 | 155 |
| 2001 | 20.6 | 156 |
| 2000 | 20.9 | 156 |
| 1999 | 21 | 158 |
| 1998 | 21.2 | 158 |
| 1997 | 21.3 | 160 |
| 1996 | 21.5 | 162 |
| 1995 | 21.6 | 164 |
| 1994 | 21.7 | 165 |
| 1993 | 21.7 | 166 |
| 1992 | 21.8 | 166 |
| 1991 | 21.9 | 165 |
| 1990 | 22.1 | 165 |
| 1989 | 22.3 | 162 |
| 1988 | 22.7 | 162 |
| 1987 | 23.1 | 160 |
| 1986 | 23.4 | 160 |