| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | - |
| 2021 | 0.363208 |
| 2020 | - |
| 2019 | - |
| 2018 | 0.00818926 |
| 2017 | - |
| 2016 | - |
| 2015 | - |
| 2014 | 0.0523193 |
| 2013 | - |
| 2012 | - |
| 2011 | - |
| 2010 | - |
| 2009 | 0.0450658 |
| 2008 | 0.551541 |
| 2007 | 0.339351 |
| 2006 | 0.382513 |
| 2005 | 0.797237 |
| 2004 | 0.569511 |
| 2003 | 0.612792 |
| 2002 | 0.302756 |
| 2001 | 0.466751 |
| 2000 | 0.579476 |
| 1999 | 0.253383 |
| 1998 | 0.211303 |
| 1997 | 0.321971 |
| 1996 | 0.30164 |
| 1995 | 0.156583 |
| 1994 | 0.240785 |
| 1993 | 0.30727 |
| 1992 | 0.214793 |
| 1991 | 0.125303 |
| 1990 | 0.161038 |
| 1989 | 0.184318 |
| 1988 | 0.179156 |
| 1987 | 0.276863 |
| 1986 | 0.0997484 |
| 1985 | 0.459518 |
| 1984 | 0.620408 |
| 1983 | 0.582813 |
| 1982 | 0.187009 |
| 1981 | 1.00605 |
| 1980 | 1.73021 |
| 1979 | 1.82311 |
| 1978 | 0.676187 |
| 1977 | 0.779328 |
| 1976 | 0.779313 |
| 1975 | 0.834989 |
| 1974 | 1.02526 |
| 1973 | 0.107643 |
| 1972 | 0.045444 |
| 1971 | 0.00255782 |
| 1970 | - |
| 1969 | - |
| 1968 | - |
| 1967 | - |
| 1966 | - |
| 1965 | - |
| 1964 | - |
| 1963 | - |
| 1962 | - |
| 1961 | - |
| 1960 | - |