| Year | Value | | 2021 | 72.268621889026 | | 2020 | 73.307521239262 | | 2019 | 73.878304949267 | | 2018 | 73.670004015973 | | 2017 | 73.424029856545 | | 2016 | 73.136069792484 | | 2015 | 72.835048496193 | | 2014 | 72.566422170586 | | 2013 | 72.278352433872 | | 2012 | 71.934483209005 | | 2011 | 71.58440911342 | | 2010 | 71.202037042478 | | 2009 | 70.902716969062 | | 2008 | 70.445023977638 | | 2007 | 70.275092259356 | | 2006 | 69.962657269221 | | 2005 | 69.535316525083 | | 2004 | 69.096218437456 | | 2003 | 68.860118979714 | | 2002 | 68.49860589793 | | 2001 | 68.1787689627 | | 2000 | 67.695643573709 | | 1999 | 67.336261935281 | | 1998 | 67.041336433176 | | 1997 | 66.681368972367 | | 1996 | 66.318583515406 | | 1995 | 66.099774787196 | | 1994 | 65.852376257855 | | 1993 | 65.63446412363 | | 1992 | 65.343818475623 | | 1991 | 65.036122882227 | | 1990 | 64.965604552128 | | 1989 | 64.743857463453 | | 1988 | 64.373392791784 | | 1987 | 64.11226737902 | | 1986 | 63.742162781932 | | 1985 | 63.27247693251 | | 1984 | 62.923469197832 | | 1983 | 62.575504650822 | | 1982 | 62.242735485666 | | 1981 | 61.796740600036 | | 1980 | 61.312483228537 | | 1979 | 60.807780100366 | | 1978 | 60.278028209417 | | 1977 | 59.751551487198 | | 1976 | 59.109730783808 | | 1975 | 58.542632084531 | | 1974 | 57.999661518188 | | 1973 | 57.479365413184 | | 1972 | 56.835127097893 | | 1971 | 56.004853970501 | | 1970 | 55.67540484406 | | 1969 | 55.322097895931 | | 1968 | 54.906464437567 | | 1967 | 54.236972921345 | | 1966 | 53.717901535484 | | 1965 | 53.154718334536 | | 1964 | 53.238290826279 | | 1963 | 52.683618498415 | | 1962 | 52.25213357841 | | 1961 | 48.936429575547 | | 1960 | 46.378406119271 |
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