Year years 1960 46.08256163154887 1961 47.35296881573248 1962 47.72240419527279 1963 48.07905137696079 1964 48.722777089289025 1965 49.33745298059658 1966 50.447382952655566 1967 50.985905657947065 1968 51.39889704324681 1969 52.05905810452625 1970 52.66791820783549 1971 53.34377649577017 1972 53.894179919123204 1973 54.744793368856286 1974 55.54285651936917 1975 56.31579812713935 1976 56.75450747748448 1977 57.95859091572013 1978 58.554677202201376 1979 59.840744612425425 1980 60.684396265449564 1981 61.33353585484996 1982 61.99857843234417 1983 63.43136436465703 1984 64.2862500446787 1985 65.07818971211444 1986 65.7668479777332 1987 66.24440656256817 1988 66.64951382621582 1989 67.0565985217515 1990 67.09742315131271 1991 68.16186735295967 1992 68.66260228952824 1993 68.96560880707858 1994 69.2980548895294 1995 69.60574031271292 1996 70.0336700870516 1997 70.32067099350859 1998 70.49337775546994 1999 70.95952170269533 2000 71.40113873964503 2001 71.72461007891202 2002 72.06374393318735 2003 72.01882243526696 2004 72.58351616069 2005 72.91249829551455 2006 73.2729595578999 2007 73.59595748899633 2008 73.68717638475135 2009 73.95348989842545 2010 74.30377683336806 2011 74.5885581881081 2012 74.59110921685713 2013 74.68923966200164 2014 74.93627217439392 2015 75.14226974616746 2016 75.56219633241247 2017 76.08603902774604 2018 76.19428399510129 2019 76.24640162107052 2020 75.32168170351457 2021 75.0848683994328 2022 75.5164789063311