| Year | Value | | 2023 | 80.861 | | 2022 | 79.79 | | 2021 | 82.098 | | 2020 | 81.904 | | 2019 | 81.763 | | 2018 | 81.629 | | 2017 | 81.383 | | 2016 | 81.105 | | 2015 | 80.858 | | 2014 | 80.497 | | 2013 | 80.109 | | 2012 | 79.672 | | 2011 | 79.247 | | 2010 | 78.738 | | 2009 | 78.19 | | 2008 | 77.716 | | 2007 | 77.313 | | 2006 | 76.967 | | 2005 | 76.61 | | 2004 | 75.845 | | 2003 | 75.97 | | 2002 | 75.717 | | 2001 | 75.591 | | 2000 | 75.244 | | 1999 | 74.975 | | 1998 | 74.685 | | 1997 | 74.506 | | 1996 | 74.255 | | 1995 | 73.909 | | 1994 | 73.6 | | 1993 | 73.267 | | 1992 | 73.016 | | 1991 | 72.706 | | 1990 | 72.384 | | 1989 | 71.919 | | 1988 | 71.481 | | 1987 | 71.04 | | 1986 | 70.492 | | 1985 | 69.761 | | 1984 | 68.878 | | 1983 | 67.967 | | 1982 | 67.218 | | 1981 | 66.575 | | 1980 | 65.917 | | 1979 | 65.291 | | 1978 | 64.689 | | 1977 | 64.165 | | 1976 | 63.51 | | 1975 | 62.722 |
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