Year years 1960 43.93002173732241 1961 48.60208060858358 1962 54.90937515987666 1963 55.47458228555039 1964 56.124168146939326 1965 56.35498710791015 1966 57.12492746298107 1967 57.836847015018705 1968 58.36241054412495 1969 58.90808792370047 1970 59.49203953286536 1971 60.2796904501774 1972 60.975989251996445 1973 61.78371315461949 1974 62.50191653080433 1975 63.176678850526116 1976 63.84671023062387 1977 64.5390121277144 1978 65.09170903193412 1979 65.69950073067365 1980 66.26355242735389 1981 66.7906673621425 1982 67.26586594983748 1983 67.7656156147249 1984 68.16932450905774 1985 68.54645906694867 1986 69.01544419125725 1987 69.38265900037324 1988 69.65819118215424 1989 69.97484619715833 1990 70.1363162947938 1991 70.26264673559632 1992 70.75034468085356 1993 71.1744583285162 1994 71.36704623274066 1995 71.76960140323348 1996 71.99415129815061 1997 72.3425015356398 1998 72.78805690560685 1999 72.87675203992981 2000 73.32236374182854 2001 74.00611446246978 2002 74.28224709083707 2003 74.53591126365677 2004 74.66736169755335 2005 75.16445607762628 2006 75.51323320991705 2007 75.78227255089024 2008 75.89897036422178 2009 76.32121022447242 2010 76.58281836721333 2011 76.87290180490649 2012 77.20914003314306 2013 77.48944013921876 2014 77.74064577921136 2015 77.95648361566776 2016 78.20850963461935 2017 78.45037572337291 2018 78.7248823195706 2019 78.91156451743747 2020 78.28847649557206 2021 77.88537942077403 2022 78.50779560124184