| Year | Value | | 2024 | 63.064 | | 2023 | 62.775 | | 2022 | 62.36 | | 2021 | 60.135 | | 2020 | 61.53 | | 2019 | 61.06 | | 2018 | 60.906 | | 2017 | 60.263 | | 2016 | 59.76 | | 2015 | 58.989 | | 2014 | 58.106 | | 2013 | 56.842 | | 2012 | 55.386 | | 2011 | 53.911 | | 2010 | 51.925 | | 2009 | 49.75 | | 2008 | 48.456 | | 2007 | 47.576 | | 2006 | 47.056 | | 2005 | 46.57 | | 2004 | 46.043 | | 2003 | 45.373 | | 2002 | 45.938 | | 2001 | 44.525 | | 2000 | 46.034 | | 1999 | 46.379 | | 1998 | 47.551 | | 1997 | 48.536 | | 1996 | 48.981 | | 1995 | 51.144 | | 1994 | 52.537 | | 1993 | 53.976 | | 1992 | 55.602 | | 1991 | 57.037 | | 1990 | 58.319 | | 1989 | 59.446 | | 1988 | 60.241 | | 1987 | 60.724 | | 1986 | 60.982 | | 1985 | 60.901 | | 1984 | 60.622 | | 1983 | 59.989 | | 1982 | 59.859 | | 1981 | 59.446 | | 1980 | 59.062 | | 1979 | 54.918 | | 1978 | 54.73 | | 1977 | 56.996 | | 1976 | 57.628 |
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