| Year | Value | | 2024 | 68.84 | | 2023 | 68.502 | | 2022 | 68.164 | | 2021 | 67.826 | | 2020 | 67.488 | | 2019 | 67.15 | | 2018 | 66.813 | | 2017 | 66.477 | | 2016 | 66.141 | | 2015 | 65.806 | | 2014 | 65.471 | | 2013 | 65.137 | | 2012 | 64.804 | | 2011 | 64.472 | | 2010 | 64.14 | | 2009 | 63.808 | | 2008 | 63.475 | | 2007 | 63.139 | | 2006 | 62.803 | | 2005 | 62.465 | | 2004 | 62.127 | | 2003 | 61.568 | | 2002 | 60.568 | | 2001 | 59.559 | | 2000 | 58.544 | | 1999 | 57.518 | | 1998 | 56.488 | | 1997 | 55.451 | | 1996 | 54.412 | | 1995 | 53.365 | | 1994 | 52.317 | | 1993 | 51.267 | | 1992 | 50.218 | | 1991 | 49.165 | | 1990 | 48.037 | | 1989 | 46.886 | | 1988 | 45.739 | | 1987 | 44.594 | | 1986 | 43.456 | | 1985 | 42.325 | | 1984 | 41.204 | | 1983 | 40.088 | | 1982 | 38.984 | | 1981 | 37.892 | | 1980 | 36.813 | | 1979 | 35.744 | | 1978 | 34.69 | | 1977 | 33.652 | | 1976 | 32.63 | | 1975 | 31.622 |
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