Year years 1960 70.19397160058537 1961 70.63204657673026 1962 70.69241725232628 1963 70.98571776174792 1964 71.50786844208541 1965 71.66183999804161 1966 71.97383326319512 1967 72.3310643373004 1968 72.33789476983107 1969 72.48734949813542 1970 72.75324256143308 1971 73.09501351014512 1972 73.38028937436174 1973 73.59265184426822 1974 73.98951506438038 1975 74.35735145384895 1976 74.65076379347516 1977 75.11817953668543 1978 75.32572921247487 1979 75.71280394185187 1980 75.74410118448058 1981 76.11539104611228 1982 76.4516666406393 1983 76.57780267285393 1984 76.90202727275205 1985 76.96881389705571 1986 77.27266943497007 1987 77.5702156210481 1988 77.71870788983259 1989 77.97837301134535 1990 78.18364345448958 1991 78.375386374348 1992 78.64005825193279 1993 78.69372815061266 1994 78.9875515932244 1995 79.04379140032039 1996 79.32878847319608 1997 79.60828467628171 1998 79.76386899757435 1999 79.8120526057524 2000 80.08435579583818 2001 80.32999960106262 2002 80.46635372537861 2003 80.55231620506811 2004 80.92549582196865 2005 81.01382737068774 2006 81.2829906342577 2007 81.47306580268864 2008 81.58735675412167 2009 81.82732409989289 2010 81.96935339929124 2011 82.18598206481795 2012 82.2963413477037 2013 82.46262823156465 2014 82.6972743504068 2015 82.54731000530522 2016 82.67701257628114 2017 82.66950134193902 2018 82.75458177135003 2019 82.97838193531233 2020 81.86804991140065 2021 81.7015519298761 2022 82.40924257777789