| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 6.7 | 14 |
| 2015 | 6.9 | 14 |
| 2014 | 7.3 | 17 |
| 2013 | 7.76 | 18 |
| 2012 | 7.86 | 22 |
| 2011 | 9.54 | 15 |
| 2010 | 10.64 | 9 |
| 2009 | 9.4 | 7 |
| 2008 | 9.65 | 14 |
| 2007 | 14.23 | 9 |
| 2006 | 12.72 | 11 |
| 2005 | 11.4 | 12 |
| 2004 | 10.11 | 23 |
| 2003 | 10.04 | 18 |
| 2002 | 9.13 | 10 |
| 2001 | 8.34 | 15 |
| 2000 | 8.49 | 22 |
| 1999 | 7.67 | 26 |
| 1998 | 7.84 | 19 |
| 1997 | 9.23 | 18 |
| 1996 | 9.93 | 17 |
| 1995 | 10.95 | 8 |
| 1994 | 13.05 | 5 |
| 1993 | 13.87 | 4 |
| 1992 | 14.22 | 4 |
| 1991 | 9.29 | 13 |
| 1990 | 3.91 | 71 |
| 1989 | 4.19 | 72 |
| 1988 | 11.23 | 15 |
| 1987 | 11.69 | 11 |
| 1986 | 8.94 | 18 |
| 1985 | 13.55 | |
| 1984 | 15.21 | |
| 1983 | 10.75 | |
| 1982 | 9.02 | |
| 1981 | 5.17 | |
| 1980 | 7.81 | |
| 1979 | 7.6 | |
| 1978 | 11.88 | |
| 1977 | 7.6 | |
| 1976 | -1.6 | |
| 1975 | 8.7 | |
| 1974 | 2.3 | |
| 1973 | 7.9 | |
| 1972 | 3.8 | |
| 1971 | 7 | |
| 1970 | 19.4 | |
| 1969 | 16.9 | |
| 1968 | -4.1 | |
| 1967 | -5.7 | |
| 1966 | 10.7 | |
| 1965 | 17 | |
| 1964 | 18.3 | |
| 1963 | 10.2 | |
| 1962 | -5.6 | |
| 1961 | -27.3 |