Year years 1960 44.62114933801577 1961 45.33694023472227 1962 45.610731155372434 1963 46.77159495383923 1964 47.44387580602521 1965 48.04629863288953 1966 48.55781965779742 1967 49.02891625109405 1968 49.453752599997856 1969 50.0577122093921 1970 50.629303447557625 1971 51.29751207668794 1972 51.86330947973145 1973 52.43405501710649 1974 53.24375653553508 1975 53.846006349484774 1976 54.281658444633266 1977 55.59957270985302 1978 56.13601604245527 1979 57.36474019739735 1980 57.71709364424082 1981 57.574552521243575 1982 58.049706816105676 1983 59.627497286312746 1984 60.93854199869379 1985 61.73435652295494 1986 62.306198301340274 1987 63.022849021655624 1988 63.39417594760988 1989 64.33416663489106 1990 64.35124668183163 1991 65.58270646227166 1992 66.15719948911143 1993 66.46992883964037 1994 66.6481408535372 1995 66.96619722403005 1996 67.35734455401546 1997 67.63385599392907 1998 67.85279909515859 1999 68.2834814735427 2000 68.64149747381033 2001 68.97329521757628 2002 69.32606751965128 2003 69.1433468828083 2004 69.6247662656893 2005 69.90737181919405 2006 70.09165495982103 2007 70.42584047921048 2008 70.68353986140755 2009 71.02221904673912 2010 71.27684185876792 2011 71.52285845816088 2012 71.37764714623262 2013 71.40574681282641 2014 71.70277902755363 2015 71.98618912427742 2016 72.2564883768439 2017 72.76700113975623 2018 72.98437341747486 2019 73.14391859259587 2020 72.17269699657263 2021 71.89987572574371 2022 72.29705086452137