Year years 1960 70.64116420296558 1961 70.95432052136259 1962 70.85918959863606 1963 71.23143503364103 1964 71.78752189776309 1965 71.80561380855808 1966 72.05867987886046 1967 72.12577680247641 1968 72.1770148221347 1969 72.05473296602902 1970 72.59705666966525 1971 72.84654287187946 1972 73.055447380382 1973 73.176980454503 1974 73.46348389902414 1975 73.4765954336938 1976 73.6205456854764 1977 73.94058487582373 1978 74.03297288705943 1979 74.18261355012423 1980 74.32521442648522 1981 74.60510778260151 1982 74.88588618728187 1983 74.92459820009881 1984 75.06090976987049 1985 75.15576364081025 1986 75.59837287608663 1987 75.83065414449108 1988 75.94753435477813 1989 76.1530245564828 1990 76.21381410459692 1991 76.16256102103615 1992 75.963461091585 1993 75.79280458936532 1994 76.09331306816978 1995 76.12429172380027 1996 76.43575309411308 1997 76.72538626569298 1998 76.97614767644554 1999 76.93650610489442 2000 77.21089196673621 2001 77.42879704212045 2002 77.50251729103246 2003 77.57277652410762 2004 78.02737667597184 2005 78.15041663919203 2006 78.57997869787361 2007 78.88122686354205 2008 79.06755117195644 2009 79.38442401536949 2010 79.60996023643675 2011 80.0695862130111 2012 80.16342425382167 2013 80.46516853881104 2014 80.76668263463229 2015 80.61905350730825 2016 80.94181397989261 2017 81.0546048431435 2018 81.18468329794561 2019 81.43027492534006 2020 80.27170417789328 2021 79.86178069100974 2022 81.0588801448828