| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | 2.0313 |
| 2021 | 2.01586 |
| 2020 | 1.81057 |
| 2019 | 2.08688 |
| 2018 | 1.47546 |
| 2017 | 1.02206 |
| 2016 | 1.07627 |
| 2015 | 1.09678 |
| 2014 | 1.12478 |
| 2013 | 1.1208 |
| 2012 | 1.23034 |
| 2011 | 1.2289 |
| 2010 | 1.15831 |
| 2009 | 1.01715 |
| 2008 | 1.11729 |
| 2007 | 1.06582 |
| 2006 | 1.03649 |
| 2005 | 1.08341 |
| 2004 | 1.13115 |
| 2003 | 1.11601 |
| 2002 | 1.04912 |
| 2001 | 0.999341 |
| 2000 | 1.01742 |
| 1999 | 1.04081 |
| 1998 | 1.09346 |
| 1997 | 1.10543 |
| 1996 | 1.24573 |
| 1995 | 1.3807 |
| 1994 | 1.54985 |
| 1993 | 1.55529 |
| 1992 | 1.54027 |
| 1991 | 1.40985 |
| 1990 | 1.57419 |
| 1989 | 1.58903 |
| 1988 | 1.72143 |
| 1987 | 1.68715 |
| 1986 | 1.65843 |
| 1985 | 1.56169 |
| 1984 | 1.61488 |
| 1983 | 1.33778 |
| 1982 | 1.36141 |
| 1981 | 1.28792 |
| 1980 | 1.39225 |
| 1979 | 1.60247 |
| 1978 | 1.66839 |
| 1977 | 1.47586 |
| 1976 | 2.00604 |
| 1975 | 1.49505 |
| 1974 | 1.29313 |
| 1973 | 1.39379 |
| 1972 | 1.63636 |
| 1971 | - |
| 1970 | - |
| 1969 | - |
| 1968 | - |
| 1967 | - |
| 1966 | - |
| 1965 | - |
| 1964 | - |
| 1963 | - |
| 1962 | - |
| 1961 | - |
| 1960 | - |