年份 | 美国 |
---|---|
2023 | - |
2022 | - |
2021 | 4.9 |
2020 | 4.9 |
2019 | 5 |
2018 | 5 |
2017 | 5.1 |
2016 | 5.2 |
2015 | 5.3 |
2014 | 5.3 |
2013 | 5.4 |
2012 | 5.5 |
2011 | 5.6 |
2010 | 5.7 |
2009 | 5.7 |
2008 | 5.8 |
2007 | 5.9 |
2006 | 6 |
2005 | 6 |
2004 | 6.1 |
2003 | 6.1 |
2002 | 6.2 |
2001 | 6.3 |
2000 | 6.4 |
1999 | 6.5 |
1998 | 6.7 |
1997 | 6.7 |
1996 | 6.9 |
1995 | 7.1 |
1994 | 7.3 |
1993 | 7.6 |
1992 | 7.8 |
1991 | 8 |
1990 | 8.3 |
1989 | 8.6 |
1988 | 8.8 |
1987 | 9 |
1986 | 9.2 |
1985 | 9.4 |
1984 | 9.7 |
1983 | 10 |
1982 | 10.4 |
1981 | 10.8 |
1980 | 11.2 |
1979 | 11.7 |
1978 | 12.2 |
1977 | 12.8 |
1976 | 13.4 |
1975 | 14 |
1974 | 14.6 |
1973 | 15.2 |
1972 | 15.9 |
1971 | 16.6 |
1970 | 17.3 |
1969 | 17.9 |
1968 | 18.5 |
1967 | 19.1 |
1966 | 19.7 |
1965 | 20.2 |
1964 | 20.8 |
1963 | 21.1 |
1962 | 21.5 |
1961 | 22.1 |
1960 | 22.4 |