| Year | Value | | 2022 | 62.50899762729 | | 2021 | 62.202861199159 | | 2020 | 61.892320669156 | | 2019 | 61.591124938895 | | 2018 | 61.29446776124 | | 2017 | 60.991760972441 | | 2016 | 60.688191763176 | | 2015 | 60.35665377943 | | 2014 | 59.949726984732 | | 2013 | 59.569423869915 | | 2012 | 59.245771449737 | | 2011 | 59.025302159951 | | 2010 | 58.804421869926 | | 2009 | 58.465279407163 | | 2008 | 58.119581433761 | | 2007 | 57.786757360581 | | 2006 | 57.452512471085 | | 2005 | 57.073415797953 | | 2004 | 56.688814790516 | | 2003 | 56.338363525077 | | 2002 | 56.000966551689 | | 2001 | 55.657428314476 | | 2000 | 55.294881401136 | | 1999 | 54.930495381244 | | 1998 | 54.567942923905 | | 1997 | 54.210271443258 | | 1996 | 53.871918461033 | | 1995 | 53.53846854638 | | 1994 | 53.185622456018 | | 1993 | 52.772255621507 | | 1992 | 52.347488739389 | | 1991 | 51.939045156012 | | 1990 | 51.598262491316 | | 1989 | 51.123506960107 | | 1988 | 50.785108222725 | | 1987 | 50.42317660275 | | 1986 | 49.971101645722 | | 1985 | 49.461348363102 | | 1984 | 48.95607207769 | | 1983 | 48.421635649301 | | 1982 | 47.890810787568 | | 1981 | 47.347463335941 | | 1980 | 46.793072071299 | | 1979 | 46.249799876089 | | 1978 | 45.769501524116 | | 1977 | 45.277438075833 | | 1976 | 44.664032044813 | | 1975 | 44.001998074784 | | 1974 | 43.377493928988 | | 1973 | 42.745659185517 | | 1972 | 42.09472508165 | | 1971 | 41.445325785233 | | 1970 | 40.807044349913 | | 1969 | 40.143742841802 | | 1968 | 39.481947482653 | | 1967 | 38.821703646746 | | 1966 | 38.182354560834 | | 1965 | 37.460415315053 | | 1964 | 36.689600287096 | | 1963 | 35.950893252865 | | 1962 | 35.220229251724 | | 1961 | 34.496314009561 | | 1960 | 33.776503946001 |
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