Year years 1960 68.86566601735709 1961 69.27412697327944 1962 69.23870068050942 1963 69.4413611052855 1964 69.92568616256374 1965 69.99542683543254 1966 70.21880251051464 1967 70.52362707352289 1968 70.35578769808014 1969 70.48224842609325 1970 70.7474216050012 1971 71.05122673722178 1972 71.25444434523021 1973 71.42484610590058 1974 71.78698934826012 1975 72.09495959322045 1976 72.36560431979574 1977 72.75000271187362 1978 72.89221309643005 1979 73.21292959790352 1980 73.24646880437938 1981 73.58769174270132 1982 73.91919738125279 1983 74.0154835542724 1984 74.28087952622623 1985 74.40277437053996 1986 74.72321321617122 1987 75.01057177782027 1988 75.11279520285643 1989 75.3524446937252 1990 75.46730731470342 1991 75.59403655248548 1992 75.70998902280702 1993 75.72228268380715 1994 76.03881249339624 1995 76.05965181487625 1996 76.4372898317012 1997 76.77489596802829 1998 76.99081498628402 1999 77.09723800997338 2000 77.34935177883399 2001 77.6440001289902 2002 77.79615349589939 2003 77.90922371271722 2004 78.33916304427439 2005 78.42641969889779 2006 78.75864735159549 2007 79.00585142774668 2008 79.15085842632047 2009 79.47560957572237 2010 79.6850584909436 2011 79.950319503711 2012 80.08367150187557 2013 80.2602095768695 2014 80.51571186995783 2015 80.38174734992552 2016 80.53913304542685 2017 80.58339260454898 2018 80.67013971213846 2019 80.89804374390012 2020 79.99832138844593 2021 79.73794490511257 2022 80.16761519140215