Year years 1960 67.30622008846895 1961 67.73093492757029 1962 67.74722692332628 1963 67.96551341998182 1964 68.4304355469184 1965 68.56490276498302 1966 68.82185704630355 1967 69.14004877225535 1968 69.0277385922928 1969 69.18057900316383 1970 69.46059390307097 1971 69.75679112631217 1972 70.0144192788676 1973 70.20084446182196 1974 70.59226768880315 1975 70.8925966100739 1976 71.16605454563141 1977 71.57613570115218 1978 71.74959366347525 1979 72.10599659970045 1980 72.17539395749907 1981 72.561832644178 1982 72.9155490753869 1983 73.05410131032683 1984 73.36365021453905 1985 73.45214433692932 1986 73.7735165596062 1987 74.06703794466631 1988 74.20764073870842 1989 74.44798455130032 1990 74.60307478720016 1991 74.79537146456492 1992 75.06615133206138 1993 75.1682268461539 1994 75.45626602556044 1995 75.54634000491255 1996 75.9198217480041 1997 76.25545147782019 1998 76.45866388328814 1999 76.57453305487263 2000 76.91642858154383 2001 77.20344117425896 2002 77.37869710126998 2003 77.50530396081248 2004 77.89854341927708 2005 78.01183133639793 2006 78.29782144410024 2007 78.50505311229972 2008 78.65647436013172 2009 78.9200247316373 2010 79.09273510945604 2011 79.31967793127642 2012 79.47425580621017 2013 79.67079969574263 2014 79.91900465470727 2015 79.79414234917732 2016 79.90687403922666 2017 79.93333514620218 2018 80.0115717465781 2019 80.22354187656556 2020 78.89938357591524 2021 78.6662054863823 2022 79.63079874536173