Year years 1960 43.42295374721574 1961 44.11603266380348 1962 44.349759174164966 1963 45.69674289780498 1964 46.39421213579038 1965 46.98998649305563 1966 47.43446441325075 1967 47.851597114019675 1968 48.29571147646362 1969 48.85086001504422 1970 49.40004567803156 1971 50.07544210542965 1972 50.64009420456531 1973 50.99178230114112 1974 51.81235622558248 1975 52.291679287879134 1976 52.78273795967643 1977 54.09029656144516 1978 54.59836975074362 1979 55.71947654114405 1980 55.67093883640497 1981 54.927617537583146 1982 55.25621990452524 1983 56.87193410702065 1984 58.50059858363863 1985 59.27823598810598 1986 59.72285529773431 1987 60.627381145890155 1988 60.96482441518121 1989 62.36323396226743 1990 62.3563688032434 1991 63.65125934507184 1992 64.28249891756772 1993 64.61689670964601 1994 64.66286430091735 1995 64.97368967486169 1996 65.33816249927204 1997 65.60131901288466 1998 65.86857394033602 1999 66.26507663238134 2000 66.53804990213467 2001 66.86890551515798 2002 67.22530161937385 2003 66.97559581525631 2004 67.38909225038083 2005 67.62149859656523 2006 67.66395890617993 2007 67.99747725478105 2008 68.4159612183542 2009 68.80733056099174 2010 69.0089253361731 2011 69.21309679014082 2012 68.97687433510015 2013 68.9725089038475 2014 69.29588469645455 2015 69.6348477604009 2016 69.74315919860197 2017 70.20444011925538 2018 70.51384736950153 2019 70.75443423515658 2020 69.76362996242952 2021 69.53146360672754 2022 69.91985493869129