Year years 1960 54.670339489705526 1961 55.228400417778595 1962 55.681348114093 1963 56.12443553656095 1964 56.62342924565543 1965 57.025246704785985 1966 57.447125332566095 1967 57.83935829643747 1968 58.22249474393282 1969 58.576025355586296 1970 58.639004828373366 1971 59.47036266643806 1972 59.83713494038427 1973 60.38916075238189 1974 60.81204396076506 1975 61.35035881830341 1976 61.583610066685324 1977 62.161060179022 1978 62.53930333717471 1979 62.89675217872346 1980 63.333652673419756 1981 63.838570139300614 1982 64.18065603151341 1983 64.74787552405014 1984 65.17264070625016 1985 65.5046498651311 1986 66.1127831799348 1987 66.54691530315246 1988 66.96856965559009 1989 67.31851608174092 1990 67.6135615180279 1991 67.97989755976408 1992 68.31907947250107 1993 68.65454665781648 1994 69.04176546534467 1995 69.35717554301614 1996 69.73645092919674 1997 70.09998133294376 1998 70.35355339362644 1999 70.76264752692664 2000 71.0805248890518 2001 71.33979396947093 2002 71.69550136933697 2003 71.88270375814392 2004 72.21107470453687 2005 72.59045551050886 2006 72.80306350769742 2007 72.94634649738931 2008 73.17223254178313 2009 73.38053577416868 2010 73.26908174486069 2011 73.7657830325408 2012 73.99658653709734 2013 74.25075158909354 2014 74.46062715024442 2015 74.5221420460803 2016 74.48903004918225 2017 74.65637969843159 2018 74.77751484072873 2019 74.97284057636965 2020 72.92992868159392 2021 72.0773193689861 2022 73.64381041784624