| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | - |
| 2021 | 8.31783 |
| 2020 | 8.19762 |
| 2019 | 9.59526 |
| 2018 | 9.34584 |
| 2017 | 9.3628 |
| 2016 | 9.61809 |
| 2015 | 9.88908 |
| 2014 | 10.4166 |
| 2013 | 11.2508 |
| 2012 | 12.0221 |
| 2011 | 12.4442 |
| 2010 | 12.3345 |
| 2009 | 11.7778 |
| 2008 | 11.972 |
| 2007 | 11.7871 |
| 2006 | 11.9965 |
| 2005 | 12.0539 |
| 2004 | 11.9685 |
| 2003 | 11.2969 |
| 2002 | 10.275 |
| 2001 | 9.55976 |
| 2000 | - |
| 1999 | - |
| 1998 | - |
| 1997 | - |
| 1996 | - |
| 1995 | - |
| 1994 | - |
| 1993 | - |
| 1992 | - |
| 1991 | - |
| 1990 | - |
| 1989 | - |
| 1988 | - |
| 1987 | - |
| 1986 | - |
| 1985 | - |
| 1984 | - |
| 1983 | - |
| 1982 | - |
| 1981 | - |
| 1980 | - |
| 1979 | - |
| 1978 | - |
| 1977 | - |
| 1976 | - |
| 1975 | - |
| 1974 | - |
| 1973 | - |
| 1972 | - |
| 1971 | - |
| 1970 | - |
| 1969 | - |
| 1968 | - |
| 1967 | - |
| 1966 | - |
| 1965 | - |
| 1964 | - |
| 1963 | - |
| 1962 | - |
| 1961 | - |
| 1960 | - |