Year years 1960 41.539846554796945 1961 46.09981682342539 1962 52.1982946865871 1963 52.673878357237925 1964 53.330992698125165 1965 53.77563275758979 1966 54.29977881606809 1967 54.733153754985935 1968 55.08085641285634 1969 55.551993901770516 1970 56.28755451740751 1971 57.03079990262338 1972 57.510716141401176 1973 58.31961004912396 1974 58.79184932355025 1975 59.49683837860893 1976 60.13537177674365 1977 60.6939331994356 1978 61.19679357020483 1979 61.67252954809712 1980 62.121642123163035 1981 62.62650213164137 1982 63.05589282231857 1983 63.418927120120394 1984 63.729317412618215 1985 64.08677573171072 1986 64.57189453962576 1987 64.85561317404463 1988 65.05893590739244 1989 65.25927758519708 1990 65.38476475602756 1991 65.67590038216909 1992 65.9613899287894 1993 66.06385409581799 1994 66.2726123789868 1995 66.51942502235337 1996 66.93291073736857 1997 67.39452707712178 1998 67.74662834158451 1999 68.02926002988836 2000 68.24127378398603 2001 68.6120144869057 2002 68.91471564198051 2003 69.31769092071319 2004 69.61721326496226 2005 70.00238641302451 2006 70.45395833237048 2007 70.73412572995143 2008 70.94609420268233 2009 71.36111242048064 2010 71.65170962925325 2011 71.987716605229 2012 72.25158380470852 2013 72.567618429048 2014 72.83781662803158 2015 73.0586759572623 2016 73.26645104433501 2017 73.33120296859131 2018 73.77774592454001 2019 74.0232409624771 2020 73.66789495146564 2021 73.40170544335078 2022 74.15914333343191