| 年份 | 美国 |
|---|---|
| 2023 | - |
| 2022 | 83.084 |
| 2021 | 82.873 |
| 2020 | 82.664 |
| 2019 | 82.459 |
| 2018 | 82.256 |
| 2017 | 82.058 |
| 2016 | 81.862 |
| 2015 | 81.671 |
| 2014 | 81.483 |
| 2013 | 81.299 |
| 2012 | 81.119 |
| 2011 | 80.944 |
| 2010 | 80.772 |
| 2009 | 80.606 |
| 2008 | 80.438 |
| 2007 | 80.269 |
| 2006 | 80.099 |
| 2005 | 79.928 |
| 2004 | 79.757 |
| 2003 | 79.583 |
| 2002 | 79.409 |
| 2001 | 79.234 |
| 2000 | 79.057 |
| 1999 | 78.742 |
| 1998 | 78.377 |
| 1997 | 78.008 |
| 1996 | 77.636 |
| 1995 | 77.257 |
| 1994 | 76.875 |
| 1993 | 76.488 |
| 1992 | 76.097 |
| 1991 | 75.701 |
| 1990 | 75.3 |
| 1989 | 75.089 |
| 1988 | 74.942 |
| 1987 | 74.793 |
| 1986 | 74.644 |
| 1985 | 74.494 |
| 1984 | 74.344 |
| 1983 | 74.194 |
| 1982 | 74.042 |
| 1981 | 73.89 |
| 1980 | 73.738 |
| 1979 | 73.692 |
| 1978 | 73.682 |
| 1977 | 73.673 |
| 1976 | 73.663 |
| 1975 | 73.653 |
| 1974 | 73.643 |
| 1973 | 73.633 |
| 1972 | 73.623 |
| 1971 | 73.613 |
| 1970 | 73.602 |
| 1969 | 73.333 |
| 1968 | 72.974 |
| 1967 | 72.612 |
| 1966 | 72.247 |
| 1965 | 71.879 |
| 1964 | 71.508 |
| 1963 | 71.134 |
| 1962 | 70.757 |
| 1961 | 70.377 |
| 1960 | 69.996 |