Year years 1960 43.015638094803016 1961 43.395855642490226 1962 43.71042067301691 1963 44.03557896543023 1964 44.51702832078213 1965 44.66610037670681 1966 44.578624746593 1967 44.99742105091334 1968 45.42200965710935 1969 45.66602412237997 1970 46.01550591426389 1971 46.52411588552485 1972 46.64124512912266 1973 47.27646337253259 1974 47.481603716626985 1975 47.86693997968956 1976 48.64620120757337 1977 49.17471748092111 1978 49.5745080069129 1979 50.00245350269365 1980 50.3576826079442 1981 50.75467863104067 1982 51.02072677843558 1983 50.17601289568202 1984 50.30743761882982 1985 50.56385163121036 1986 50.969234027512314 1987 51.452350645214665 1988 51.17649257585347 1989 51.91142452309702 1990 51.93566459775717 1991 51.71728852465928 1992 51.52583489059079 1993 51.77750465706595 1994 51.87817550144703 1995 52.013561884896895 1996 51.92219157810899 1997 52.03151946107882 1998 51.81229346993793 1999 52.442602012048596 2000 52.752335122315756 2001 52.93456251814286 2002 53.27624732338937 2003 53.70586636054043 2004 54.16620577494057 2005 54.786753254528705 2006 55.53172059547608 2007 56.21272296281418 2008 56.836895896882154 2009 57.69446996428965 2010 58.35371241817716 2011 59.13999921811031 2012 59.78076829261686 2013 60.39581244089927 2014 60.923721386700045 2015 61.36737034972571 2016 61.88664687953525 2017 62.30545312471536 2018 62.72843317688088 2019 63.13765185559283 2020 62.828838645803785 2021 62.277173992766585 2022 62.77167295947984