Year years 1960 56.86465866497022 1961 57.27841853496934 1962 57.80765989852569 1963 58.013029966842474 1964 58.58586035678651 1965 59.226443739854496 1966 59.50379604243297 1967 59.782573479616 1968 60.07009535825693 1969 60.247332276249516 1970 60.61631512355745 1971 60.895835286812556 1972 61.19168708576344 1973 61.44619851912587 1974 60.76527838234529 1975 61.14450874229621 1976 61.52576364070261 1977 61.73697742832019 1978 61.79889127356378 1979 62.089385521557126 1980 62.72465944950435 1981 63.02381316314044 1982 63.28586059229385 1983 63.524354242349645 1984 64.02188404125911 1985 64.30662256183413 1986 64.58714945277993 1987 64.98771403834934 1988 65.24797617288412 1989 65.79552326140002 1990 65.91177214105629 1991 65.96580668706103 1992 66.0338725141068 1993 66.1812534634853 1994 66.01564703454858 1995 66.15655932779197 1996 66.40835703069759 1997 66.44304291234319 1998 66.40823717241523 1999 66.29736650603927 2000 67.21507371114718 2001 67.43925743577243 2002 67.54299776602845 2003 67.73386841739246 2004 68.0104522277905 2005 68.3086990510631 2006 68.62130838419762 2007 68.97895157779527 2008 69.35118421875052 2009 69.72013657992471 2010 70.19381162653578 2011 70.50948128113215 2012 70.83308164349344 2013 71.17370558901608 2014 71.45436765339079 2015 71.73742744338064 2016 72.06530972093037 2017 72.41399843804297 2018 72.6308564795014 2019 72.75062706426235 2020 72.54059803701163 2021 71.6444984379684 2022 72.16452552417641