Year years 1960 44.62114933801577 1961 45.33694023472228 1962 45.61073115537241 1963 46.77159495383925 1964 47.443875806025204 1965 48.04629863288955 1966 48.557819657797424 1967 49.02891625109405 1968 49.45375259999787 1969 50.05771220939211 1970 50.62930344755763 1971 51.297512076687944 1972 51.863309479731456 1973 52.43405501710649 1974 53.24375653553508 1975 53.846006349484774 1976 54.28165844463327 1977 55.59957270985302 1978 56.13601604245527 1979 57.36474019739737 1980 57.71709364424083 1981 57.574552521243575 1982 58.04970681610567 1983 59.627497286312746 1984 60.9385419986938 1985 61.73435652295494 1986 62.306198301340274 1987 63.022849021655624 1988 63.39417594760989 1989 64.33416663489105 1990 64.32000573503255 1991 65.55854402918055 1992 66.13515514008148 1993 66.44784335452457 1994 66.62188673358526 1995 66.9399820546723 1996 67.33045613724897 1997 67.60563056104932 1998 67.82423611595998 1999 68.25689501632309 2000 68.62333389324165 2001 68.96373624030834 2002 69.30874848869513 2003 69.1230574789837 2004 69.60811601535512 2005 69.88413732115588 2006 70.0719112166503 2007 70.40701384924307 2008 70.6645249982073 2009 71.00465042818414 2010 71.25758184250935 2011 71.50354786792096 2012 71.3540519418564 2013 71.37597721520234 2014 71.69231407034749 2015 71.95855146640594 2016 72.23013227963254 2017 72.74322854556864 2018 72.96338905762993 2019 73.11939012664116 2020 72.14637619842054 2021 71.8811305367081 2022 72.28325411622335