| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | 54.0537 |
| 2021 | 53.6616 |
| 2020 | 53.2209 |
| 2019 | 52.7364 |
| 2018 | 52.2272 |
| 2017 | 51.7962 |
| 2016 | 51.1636 |
| 2015 | 50.6589 |
| 2014 | 50.5094 |
| 2013 | 50.2134 |
| 2012 | 49.7604 |
| 2011 | 49.2849 |
| 2010 | 49.0203 |
| 2009 | 48.9493 |
| 2008 | 48.8241 |
| 2007 | 48.7498 |
| 2006 | 48.9016 |
| 2005 | 49.1893 |
| 2004 | 49.5221 |
| 2003 | 49.8584 |
| 2002 | 50.2119 |
| 2001 | 50.5623 |
| 2000 | 50.9275 |
| 1999 | 51.3356 |
| 1998 | 51.6327 |
| 1997 | 51.8889 |
| 1996 | 52.1392 |
| 1995 | 52.3139 |
| 1994 | 52.311 |
| 1993 | 52.1744 |
| 1992 | 51.9499 |
| 1991 | 51.5399 |
| 1990 | 51.1513 |
| 1989 | 50.87 |
| 1988 | 50.3981 |
| 1987 | 49.9658 |
| 1986 | 49.9119 |
| 1985 | 50.0221 |
| 1984 | 50.0901 |
| 1983 | 50.2248 |
| 1982 | 50.4462 |
| 1981 | 50.6223 |
| 1980 | 50.9461 |
| 1979 | 51.5164 |
| 1978 | 52.2703 |
| 1977 | 53.125 |
| 1976 | 54.071 |
| 1975 | 55.1783 |
| 1974 | 56.3774 |
| 1973 | 57.6466 |
| 1972 | 59.0041 |
| 1971 | 60.3297 |
| 1970 | 61.5171 |
| 1969 | 62.6664 |
| 1968 | 63.9197 |
| 1967 | 64.9402 |
| 1966 | 66.2026 |
| 1965 | 67.0416 |
| 1964 | 66.8327 |
| 1963 | 66.739 |
| 1962 | 67.0072 |
| 1961 | 67.2868 |
| 1960 | 66.7932 |