| Year | Value | | 2024 | 78.264 | | 2023 | 78.085 | | 2022 | 77.629 | | 2021 | 73.201 | | 2020 | 77.407 | | 2019 | 77.413 | | 2018 | 77.426 | | 2017 | 77.3 | | 2016 | 77.571 | | 2015 | 77.745 | | 2014 | 77.825 | | 2013 | 78.028 | | 2012 | 78.162 | | 2011 | 78.051 | | 2010 | 77.876 | | 2009 | 77.584 | | 2008 | 77.589 | | 2007 | 77.55 | | 2006 | 77.406 | | 2005 | 77.54 | | 2004 | 77.326 | | 2003 | 77.405 | | 2002 | 76.766 | | 2001 | 76.429 | | 2000 | 75.922 | | 1999 | 75.719 | | 1998 | 75.412 | | 1997 | 75.064 | | 1996 | 74.69 | | 1995 | 74.346 | | 1994 | 74.092 | | 1993 | 73.874 | | 1992 | 73.846 | | 1991 | 73.757 | | 1990 | 73.823 | | 1989 | 73.69 | | 1988 | 73.724 | | 1987 | 73.596 | | 1986 | 73.558 | | 1985 | 73.464 | | 1984 | 73.552 | | 1983 | 73.564 | | 1982 | 73.439 | | 1981 | 72.996 | | 1980 | 72.603 | | 1979 | 72.272 | | 1978 | 71.89 | | 1977 | 71.411 | | 1976 | 70.878 |
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