Year years 1960 64.28 1961 62.054 1962 60.428 1963 63.027 1964 65.066 1965 65.375 1966 60.461 1967 64.388 1968 65.016 1969 64.665 1970 64.799 1971 64.812 1972 66.198 1973 68.424 1974 68.821 1975 68.908 1976 68.311 1977 68.316 1978 69.02 1979 69.9 1980 69.453 1981 69.829 1982 69.518 1983 70.14 1984 71.385 1985 70.245 1986 69.436 1987 70.004 1988 70.808 1989 70.77 1990 70.643 1991 70.96 1992 71.114 1993 70.464 1994 70.846 1995 72.616 1996 75.095 1997 74.358 1998 76.684 1999 75.83 2000 75.293 2001 75.701 2002 78.669 2003 77.079 2004 77.112 2005 74.349 2006 73.954 2007 75.137 2008 75.425 2009 76.827 2010 75.921 2011 77.138 2012 76.796 2013 76.017 2014 76.262 2015 76.427 2016 76.231 2017 79.119 2018 77.594 2019 77.791 2020 77.885 2021 75.817 2022 78.435