| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | 7.04072 |
| 2021 | 4.49279 |
| 2020 | 1.30491 |
| 2019 | 1.79393 |
| 2018 | 2.40406 |
| 2017 | 1.89961 |
| 2016 | 1.00224 |
| 2015 | 1.00054 |
| 2014 | 1.86989 |
| 2013 | 1.75095 |
| 2012 | 1.8706 |
| 2011 | 2.07771 |
| 2010 | 1.20179 |
| 2009 | 0.640955 |
| 2008 | 1.91793 |
| 2007 | 2.70253 |
| 2006 | 3.08558 |
| 2005 | 3.13582 |
| 2004 | 2.68441 |
| 2003 | 1.9736 |
| 2002 | 1.55853 |
| 2001 | 2.25295 |
| 2000 | 2.26555 |
| 1999 | 1.40923 |
| 1998 | 1.12553 |
| 1997 | 1.72443 |
| 1996 | 1.83097 |
| 1995 | 2.0969 |
| 1994 | 2.13542 |
| 1993 | 2.37034 |
| 1992 | 2.27891 |
| 1991 | 3.38176 |
| 1990 | 3.74333 |
| 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 | - |