Year years 1960 45.93245360612966 1961 46.66480759417704 1962 46.99663276922009 1963 47.92410657724617 1964 48.55996064895848 1965 49.16958412642579 1966 49.753567807951704 1967 50.28723776713337 1968 50.68252557703438 1969 51.33990839041214 1970 51.93123095900361 1971 52.582163332112 1972 53.14512343011851 1973 53.96253454702556 1974 54.757954186532366 1975 55.521620334992804 1976 55.91370263661964 1977 57.173957821312996 1978 57.74075333732435 1979 59.08360167259816 1980 59.92114474010615 1981 60.57391277993667 1982 61.2574057703384 1983 62.76399560969953 1984 63.64532948090524 1985 64.45405746725886 1986 65.17337982245748 1987 65.64419843526049 1988 66.08482659429181 1989 66.41956840726077 1990 66.43085932706468 1991 67.57045945646273 1992 68.07256165703969 1993 68.35852724880306 1994 68.68448141664078 1995 69.00677110327021 1996 69.43736593054462 1997 69.73008058780273 1998 69.89458770100113 1999 70.37087305737235 2000 70.82122788002889 2001 71.15051117029381 2002 71.49414774741248 2003 71.39737352016365 2004 71.96015430765969 2005 72.30334941758969 2006 72.6693697972654 2007 73.0035111210499 2008 73.05526479668825 2009 73.32137206035718 2010 73.64090031027929 2011 73.93242968152195 2012 73.89564618381212 2013 73.96797683682394 2014 74.23155428192244 2015 74.4390402856514 2016 74.89553930934017 2017 75.47086862646495 2018 75.57323067654347 2019 75.62756314013016 2020 74.7095540396599 2021 74.40676666208009 2022 74.80260179210383