| Year | Value | | 2024 | 66.289 | | 2023 | 66.035 | | 2022 | 65.617 | | 2021 | 60.417 | | 2020 | 61.454 | | 2019 | 62.941 | | 2018 | 62.443 | | 2017 | 62.406 | | 2016 | 62.646 | | 2015 | 62.27 | | 2014 | 62.26 | | 2013 | 62.188 | | 2012 | 61.735 | | 2011 | 61.25 | | 2010 | 60.702 | | 2009 | 60.248 | | 2008 | 59.708 | | 2007 | 58.956 | | 2006 | 58.553 | | 2005 | 58.247 | | 2004 | 57.81 | | 2003 | 57.171 | | 2002 | 56.225 | | 2001 | 55.511 | | 2000 | 55.005 | | 1999 | 54.532 | | 1998 | 52.487 | | 1997 | 53.212 | | 1996 | 52.83 | | 1995 | 52.103 | | 1994 | 50.969 | | 1993 | 51.021 | | 1992 | 46.569 | | 1991 | 45.521 | | 1990 | 45.118 | | 1989 | 44.496 | | 1988 | 43.238 | | 1987 | 38.831 | | 1986 | 38.4 | | 1985 | 32.132 | | 1984 | 31.473 | | 1983 | 36.517 | | 1982 | 36.058 | | 1981 | 39.406 | | 1980 | 39.258 | | 1979 | 38.844 | | 1978 | 40.086 | | 1977 | 41.082 | | 1976 | 40.518 |
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