Year years 1960 45.85353124227925 1961 46.228114474051594 1962 46.65241257987056 1963 46.93913792355676 1964 47.36352301158992 1965 46.83911286910283 1966 47.331982007987804 1967 47.62825494012021 1968 48.657105310836734 1969 49.09749693618914 1970 49.044095185871925 1971 48.13455060267811 1972 50.08557370238925 1973 50.658267153471186 1974 51.086778836225754 1975 51.73290071772709 1976 52.26098986220158 1977 52.91134023265837 1978 53.43383071292158 1979 53.9412101604931 1980 54.47853916090759 1981 54.97370178790862 1982 55.39957181780072 1983 55.87940218671367 1984 56.314548198645 1985 56.70954981157481 1986 57.102880622962104 1987 57.474568443837626 1988 57.83927813354706 1989 58.20718666696068 1990 58.58834425996162 1991 58.770002701031444 1992 59.19776947417034 1993 59.449121167671734 1994 59.740527464614274 1995 60.040352110720576 1996 60.32947158615023 1997 60.72921956014153 1998 61.16108682800289 1999 61.676900668204816 2000 61.986693399631584 2001 62.333082041944586 2002 62.756300657551535 2003 63.14981758550745 2004 63.470697201824876 2005 63.84852468026285 2006 64.25545671894943 2007 64.5325590363024 2008 64.71817362009341 2009 65.16021582555715 2010 65.52809613924398 2011 65.97131511835687 2012 66.38216172697845 2013 66.79100930591447 2014 67.2288182812778 2015 67.62558980111237 2016 68.00928780799063 2017 68.3334812907 2018 68.57630437240715 2019 68.77964051700751 2020 68.24464181566492 2021 66.53281261853186 2022 67.1969794891736