| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 14.3 | 181 |
| 2015 | 14.5 | 179 |
| 2014 | 14.6 | 178 |
| 2013 | 14.8 | 175 |
| 2012 | 14.9 | 174 |
| 2011 | 15 | 176 |
| 2010 | 14.9 | 176 |
| 2009 | 15 | 177 |
| 2008 | 15 | 178 |
| 2007 | 15 | 181 |
| 2006 | 15 | 182 |
| 2005 | 15.1 | 184 |
| 2004 | 15.1 | 185 |
| 2003 | 15.1 | 188 |
| 2002 | 15.2 | 189 |
| 2001 | 15.3 | 190 |
| 2000 | 15.4 | 191 |
| 1999 | 15.7 | 191 |
| 1998 | 16.1 | 190 |
| 1997 | 16.5 | 190 |
| 1996 | 16.9 | 190 |
| 1995 | 17.2 | 189 |
| 1994 | 17.7 | 186 |
| 1993 | 18.2 | 184 |
| 1992 | 18.7 | 182 |
| 1991 | 19.2 | 181 |
| 1990 | 19.8 | 180 |
| 1989 | 20.3 | 176 |
| 1988 | 20.8 | 176 |
| 1987 | 21.3 | 173 |
| 1986 | 21.7 | 171 |