Year years 1960 56.98985918611615 1961 57.54862194787619 1962 58.01254937173683 1963 58.46095472508464 1964 58.97355359182776 1965 59.425755627042356 1966 59.82975423584859 1967 60.24119204657744 1968 60.65403018544037 1969 61.0182551209888 1970 61.04455917994101 1971 61.943923332342536 1972 62.35437466091401 1973 62.951131101129015 1974 63.37647588211212 1975 63.99019623570611 1976 64.25913103657255 1977 64.95606176773789 1978 65.40981852317046 1979 65.8238887909342 1980 66.26300823263759 1981 66.84140808412467 1982 67.2114795089437 1983 67.73767297844785 1984 68.1718252974203 1985 68.43162328497203 1986 69.07636933407137 1987 69.54610882322002 1988 69.97708326521804 1989 70.41024666555337 1990 70.81919332865259 1991 71.20078105716095 1992 71.5512936933443 1993 71.89725307699509 1994 72.24921650183826 1995 72.60168961072677 1996 72.9706889857776 1997 73.34046562805219 1998 73.55755491846695 1999 73.97563304725266 2000 74.43070368736163 2001 74.71025951797009 2002 75.0407605373329 2003 75.13903168795498 2004 75.47588290618695 2005 75.81135812485512 2006 76.01814312663942 2007 76.1549162758344 2008 76.36098178605539 2009 76.5409742362351 2010 76.41408008316188 2011 76.90463109095138 2012 77.15963756501147 2013 77.35345918462738 2014 77.5216179254434 2015 77.63373362189937 2016 77.68316993256178 2017 77.75886015167873 2018 77.90376003140156 2019 78.11515099643347 2020 76.49814383464684 2021 75.63956152516377 2022 76.82881661657845