| Year | Value | | 2022 | 66.090233582655 | | 2021 | 65.806702530684 | | 2020 | 65.560045311846 | | 2019 | 65.313169246354 | | 2018 | 65.021226998198 | | 2017 | 64.711306676216 | | 2016 | 64.3994716194 | | 2015 | 64.057370079665 | | 2014 | 63.653466483498 | | 2013 | 63.275531203013 | | 2012 | 62.931326503097 | | 2011 | 62.671849567751 | | 2010 | 62.417797317701 | | 2009 | 62.040451987656 | | 2008 | 61.609450185736 | | 2007 | 61.175352574965 | | 2006 | 60.742251792675 | | 2005 | 60.293924061392 | | 2004 | 59.8871122286 | | 2003 | 59.539290474856 | | 2002 | 59.199876877001 | | 2001 | 58.852468213592 | | 2000 | 58.483842657604 | | 1999 | 58.11450111365 | | 1998 | 57.745189341605 | | 1997 | 57.380623828163 | | 1996 | 57.031795430828 | | 1995 | 56.692427535664 | | 1994 | 56.346599117685 | | 1993 | 55.942014979345 | | 1992 | 55.502563668465 | | 1991 | 55.013775779328 | | 1990 | 54.671390343776 | | 1989 | 54.291863491321 | | 1988 | 53.909237359647 | | 1987 | 53.505283327605 | | 1986 | 53.023176527739 | | 1985 | 52.459836718632 | | 1984 | 51.898444477044 | | 1983 | 51.313115311812 | | 1982 | 50.717544473791 | | 1981 | 50.114520290419 | | 1980 | 49.494612697675 | | 1979 | 48.86480899403 | | 1978 | 48.281529371608 | | 1977 | 47.688940630842 | | 1976 | 46.995737891231 | | 1975 | 46.262850116958 | | 1974 | 45.561145836482 | | 1973 | 44.830723139375 | | 1972 | 44.075117094643 | | 1971 | 43.334253676671 | | 1970 | 42.600596333835 | | 1969 | 41.843414781221 | | 1968 | 41.096428416921 | | 1967 | 40.361405642752 | | 1966 | 39.632477368767 | | 1965 | 38.846180549516 | | 1964 | 38.010929737618 | | 1963 | 37.203545741499 | | 1962 | 36.421823711959 | | 1961 | 35.651174521775 | | 1960 | 34.89256859534 |
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