Year years 1960 71.749 1961 72.38 1962 72.583 1963 72.725 1964 73.352 1965 73.293 1966 73.458 1967 73.725 1968 73.362 1969 73.303 1970 73.547 1971 73.795 1972 74.111 1973 74.334 1974 74.593 1975 74.504 1976 74.958 1977 75.612 1978 75.633 1979 75.962 1980 76.147 1981 76.349 1982 76.645 1983 76.934 1984 77.357 1985 77.461 1986 77.638 1987 78.103 1988 78.286 1989 78.466 1990 78.419 1991 78.7 1992 79.2 1993 79.2 1994 79.6 1995 79.7 1996 79.9 1997 80.3 1998 80.6 1999 80.8 2000 81 2001 81.3 2002 81.2 2003 81.3 2004 81.6 2005 81.8 2006 82 2007 82.3 2008 82.4 2009 82.5 2010 82.6 2011 83.1 2012 83.1 2013 83 2014 83.6 2015 83.1 2016 83.5 2017 83.4 2018 83.3 2019 83.7 2020 83.5 2021 83.3 2022 83.2