Year years 1960 46.22789132098803 1961 46.54233098338957 1962 46.88527694324949 1963 47.187179156833324 1964 47.69949531899309 1965 47.807094707005014 1966 47.777304026955306 1967 48.01519102770275 1968 48.44030123979095 1969 48.542218831156276 1970 48.92553698087063 1971 49.50009731007087 1972 49.50700378935333 1973 50.103297980453526 1974 50.23734077964083 1975 50.484002715741326 1976 50.947728339706366 1977 51.47797304369472 1978 51.60926316385559 1979 51.85304977037558 1980 52.07609251920815 1981 52.209476258461656 1982 52.188225280840385 1983 51.58250837359558 1984 51.434756934589075 1985 51.608280044030145 1986 52.2318694997475 1987 52.679929722592256 1988 52.2507895423155 1989 53.28316471692036 1990 53.30253431575152 1991 53.30873661822025 1992 53.281669542089084 1993 53.67282525079816 1994 54.28838789778534 1995 54.00329615791167 1996 54.081087533764446 1997 54.3782007379501 1998 54.164337000250846 1999 54.87923102629131 2000 55.509639316699236 2001 55.72925521503298 2002 56.14948004720196 2003 56.419036453388344 2004 56.665498658649 2005 57.05810557151295 2006 57.54270914152649 2007 58.00940644920565 2008 58.01868742884508 2009 59.06225345394925 2010 59.3081381864351 2011 59.96632784371176 2012 60.16658424279599 2013 60.46601388694744 2014 60.70998735538693 2015 61.01446364341172 2016 61.292380360629714 2017 61.657084412036525 2018 61.9720515279674 2019 62.269780743055236 2020 61.762486987637644 2021 61.253265735449126 2022 61.79258830055621