Year years 1960 55.92668863015541 1961 56.723147441911735 1962 57.55657510261113 1963 58.291813763835435 1964 58.56992532569721 1965 59.75856799677115 1966 60.35692309934758 1967 60.94911577068673 1968 61.52896408306392 1969 61.925163474249956 1970 62.40656316015184 1971 62.8350144236247 1972 63.19103127978263 1973 63.21204773410299 1974 63.771543945576916 1975 63.82142197842687 1976 64.57019443714867 1977 64.84218899715331 1978 65.3386011865916 1979 65.75569445175896 1980 65.81415448661677 1981 65.96453936780772 1982 66.19138032417976 1983 66.66217840604597 1984 67.14461057019847 1985 67.56895993168715 1986 67.72401599723044 1987 68.01479898741472 1988 68.35603366281775 1989 68.4638518154591 1990 68.72381873572499 1991 68.80596548460973 1992 68.97219551329198 1993 69.09400706822714 1994 69.29031849833417 1995 69.51535805859915 1996 69.59909709300072 1997 69.68304869182732 1998 69.89116764737818 1999 69.92959646555687 2000 69.89301774339806 2001 69.92957449516392 2002 69.64921673221113 2003 69.92187200630902 2004 70.03555515934302 2005 70.14119741093634 2006 70.22192417693172 2007 70.15066507718345 2008 70.33150244256994 2009 70.17888097441809 2010 70.56061292334837 2011 70.7084790521307 2012 70.70220843507175 2013 70.75367065652193 2014 70.75476329971018 2015 70.70235097915341 2016 70.89424300130275 2017 71.17832724888002 2018 71.26162342902907 2019 71.3253170902613 2020 71.37340810636216 2021 71.20008602913511 2022 71.85068033105394