Year years 1960 71.169 1961 71.303 1962 71.414 1963 71.518 1964 71.628 1965 71.76 1966 71.912 1967 72.066 1968 72.235 1969 72.386 1970 72.519 1971 72.634 1972 72.734 1973 72.859 1974 72.991 1975 73.15 1976 73.34 1977 73.558 1978 73.805 1979 74.081 1980 74.388 1981 74.72 1982 75.063 1983 75.406 1984 75.738 1985 76.047 1986 76.329 1987 76.586 1988 76.819 1989 77.034 1990 77.236 1991 77.431 1992 77.625 1993 77.826 1994 78.039 1995 78.273 1996 78.526 1997 78.789 1998 79.053 1999 79.308 2000 79.546 2001 79.761 2002 79.949 2003 80.119 2004 80.263 2005 80.376 2006 80.488 2007 80.58 2008 80.675 2009 80.776 2010 80.897 2011 81.032 2012 81.165 2013 81.28 2014 81.36 2015 81.386 2016 81.356 2017 81.316 2018 81.283 2019 81.296 2020 81.911 2021 79.258 2022 81.685