Year years 1960 43.87914755029954 1961 46.24208438731099 1962 49.30224363035189 1963 49.74252607215967 1964 50.276136110103465 1965 49.95070335823609 1966 50.6698020296331 1967 51.12705780382084 1968 51.79106045707413 1969 52.18825995264105 1970 52.55769028716219 1971 52.49999650467248 1972 53.701933599962366 1973 54.32810403307229 1974 54.76218431845462 1975 55.26878888105535 1976 55.79291858426924 1977 56.2653125048974 1978 56.65169900398263 1979 57.07956371513209 1980 57.460468006855955 1981 57.82488302575335 1982 58.19357729753869 1983 58.488774614556704 1984 58.822605843868416 1985 59.2088631964995 1986 59.66983271377324 1987 59.99359321426439 1988 60.18100992880008 1989 60.57979978016196 1990 60.75900647712576 1991 60.99016258628897 1992 61.25835544426008 1993 61.443105286181456 1994 61.73618405084388 1995 62.01331163867912 1996 62.31719610673657 1997 62.679168505450576 1998 62.95812081379586 1999 63.34134244453612 2000 63.6575275576536 2001 63.95667948288235 2002 64.27694294594136 2003 64.5335091534392 2004 64.76582863115576 2005 65.12428584148851 2006 65.49078515423226 2007 65.7408753460342 2008 65.93371503396644 2009 66.32703875019087 2010 66.6227465676397 2011 66.97663541047322 2012 67.26842141291071 2013 67.5805579666978 2014 67.93466164699672 2015 68.23757411190661 2016 68.50223335255005 2017 68.70400314284352 2018 69.00448490293107 2019 69.20218924685491 2020 68.41564806608801 2021 67.40697361165569 2022 68.14770800204589