Year years 1960 36.30122141847951 1961 41.68908465427287 1962 49.12405861307014 1963 49.61290354200674 1964 50.31837483893168 1965 50.01508394266792 1966 51.375194635169144 1967 52.26971117080447 1968 52.735554815873364 1969 53.456456257534526 1970 54.14819259473882 1971 55.03914850043419 1972 55.60827289951089 1973 56.533949492808325 1974 57.093803682490645 1975 57.88500546677664 1976 58.7261431960772 1977 59.42983546213187 1978 60.01443573085967 1979 60.61921438622123 1980 61.15352549758095 1981 61.65684549499006 1982 62.12680976774286 1983 62.51748619077803 1984 62.92340057396075 1985 63.2986643648422 1986 63.605279763647154 1987 63.9495878094147 1988 64.2075455185606 1989 64.53015469423033 1990 64.78857337544204 1991 65.16920792374572 1992 65.64170324782027 1993 66.01029136521235 1994 66.36959927627204 1995 66.62687699693292 1996 66.92256326804822 1997 67.31441875098687 1998 67.64789234742422 1999 67.99094249043415 2000 68.31252426375121 2001 68.68128955939719 2002 69.04922619672979 2003 69.43950120801296 2004 69.57244460290413 2005 70.05831589728376 2006 70.40754476164891 2007 70.62919460051732 2008 70.64013524037175 2009 71.10769280517671 2010 71.35035518847161 2011 71.6074154164697 2012 71.82292370864815 2013 72.04984163858553 2014 72.31150540453157 2015 72.51962544024914 2016 72.68097199917729 2017 72.6288528507143 2018 73.10947939821179 2019 73.33016592143096 2020 73.20046074677393 2021 72.82485121210543 2022 73.53240854126666