Year years 1960 42.85411092770643 1961 43.36649687296321 1962 43.954763473139025 1963 44.27146748326769 1964 44.931809805846434 1965 45.11924658411779 1966 45.60364732337895 1967 46.033639091292386 1968 46.55012988193936 1969 46.901187313605526 1970 46.4146636159612 1971 44.12184393530119 1972 47.87693963934154 1973 48.407028411839875 1974 48.51528682606687 1975 48.70091663897487 1976 49.277955178212416 1977 49.85860072215302 1978 50.22902555633006 1979 50.657288013690746 1980 51.16313327085992 1981 51.542985599446325 1982 51.76971429525569 1983 51.56515401299903 1984 51.70436056188602 1985 51.948304486562414 1986 52.36853937787926 1987 52.72615839119904 1988 52.68860031356102 1989 53.325337983209344 1990 53.55564679079413 1991 53.322289109238326 1992 53.64322072552884 1993 53.888748218787654 1994 54.234642399318496 1995 54.42999144647849 1996 54.565797804637704 1997 55.00914742548013 1998 55.24799411024841 1999 56.187800595524536 2000 56.63170080245032 2001 57.01124339586935 2002 57.4175623707504 2003 57.85886586840762 2004 58.179602996072205 2005 58.60053948424088 2006 59.23873613693904 2007 59.5910104996775 2008 59.773684274088815 2009 60.451432222413345 2010 60.89852696243462 2011 61.455360850920115 2012 61.77098085570556 2013 62.10515024469133 2014 62.4180887324393 2015 62.75171706141373 2016 63.16565331525459 2017 63.54116945810773 2018 63.88110119695857 2019 64.21240643971596 2020 63.748248344655764 2021 63.40066424565102 2022 64.04892352081865