Year years 1960 43.82888779516641 1961 44.327609296761146 1962 44.79221739780898 1963 44.96964881205251 1964 45.688396180369175 1965 45.70800350162564 1966 46.07654237777135 1967 46.71206963397455 1968 47.07163168709481 1969 47.33964511156205 1970 46.239227878092436 1971 45.07324445432727 1972 47.98513742176579 1973 48.539584077645834 1974 48.48040138186565 1975 48.43625914521985 1976 48.988558299136535 1977 49.74908718366451 1978 50.26032751895383 1979 50.772407311039466 1980 51.23250938276051 1981 51.5422449586497 1982 51.84895195931574 1983 51.340230876591676 1984 51.61368238809167 1985 51.97062627676364 1986 52.61047112353782 1987 53.25068880777824 1988 53.12493712059841 1989 53.84858542031835 1990 54.14135801862628 1991 53.82401579295257 1992 54.50381020384531 1993 54.950773950563125 1994 55.42004671124598 1995 55.89271097247322 1996 55.969841746180194 1997 56.71432159520268 1998 57.109484039423606 1999 58.19827234818386 2000 58.51754473866193 2001 58.9924364994037 2002 59.51384897154097 2003 60.0858318494903 2004 60.35463103927097 2005 61.068583811700094 2006 61.64090167508662 2007 62.09568993361022 2008 62.197273124133865 2009 63.16434874594579 2010 63.67434219195593 2011 64.40753833970778 2012 64.9656637916554 2013 65.51781628748189 2014 65.83110790374742 2015 66.22432979323587 2016 66.77828929596396 2017 67.19384252031674 2018 67.59020233896821 2019 68.02489513407721 2020 67.47043980975964 2021 67.1679415857136 2022 67.90977060719128