| Year | Value | | 2021 | 74.052 | | 2020 | 74.808 | | 2019 | 76.004 | | 2018 | 75.733 | | 2017 | 76.593 | | 2016 | 75.742 | | 2015 | 74.62 | | 2014 | 75.24 | | 2013 | 75.059 | | 2012 | 74.484 | | 2011 | 74.257 | | 2010 | 73.499 | | 2009 | 73.088 | | 2008 | 72.508 | | 2007 | 72.835 | | 2006 | 72.239 | | 2005 | 72.68 | | 2004 | 71.999 | | 2003 | 71.429 | | 2002 | 70.705 | | 2001 | 69.929 | | 2000 | 68.618 | | 1999 | 67.569 | | 1998 | 66.993 | | 1997 | 66.378 | | 1996 | 65.763 | | 1995 | 64.093 | | 1994 | 65.25 | | 1993 | 65.312 | | 1992 | 65.318 | | 1991 | 65.176 | | 1990 | 65.023 | | 1989 | 64.446 | | 1988 | 64.058 | | 1987 | 63.404 | | 1986 | 62.747 | | 1985 | 62.182 | | 1984 | 61.661 | | 1983 | 61.693 | | 1982 | 61.67 | | 1981 | 61.593 | | 1980 | 61.368 | | 1979 | 60.917 | | 1978 | 60.306 | | 1977 | 59.568 | | 1976 | 58.65 | | 1975 | 57.89 | | 1974 | 56.837 | | 1973 | 56.008 | | 1972 | 55.309 | | 1971 | 54.813 | | 1970 | 54.333 | | 1969 | 53.736 | | 1968 | 53.176 | | 1967 | 52.722 | | 1966 | 52.356 | | 1965 | 51.808 | | 1964 | 51.345 | | 1963 | 50.894 | | 1962 | 50.392 | | 1961 | 49.953 | | 1960 | 49.411 |
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