Year | Value | 2022 | 51.838213958199 | 2021 | 51.821606883358 | 2020 | 51.802215409854 | 2019 | 51.773574869338 | 2018 | 51.744238257221 | 2017 | 51.712027253875 | 2016 | 51.675872677662 | 2015 | 51.63772537052 | 2014 | 51.597312492499 | 2013 | 51.551825603135 | 2012 | 51.503760239199 | 2011 | 51.431793766587 | 2010 | 51.328111585148 | 2009 | 51.21005628372 | 2008 | 51.087914738517 | 2007 | 50.971765788097 | 2006 | 50.860633738932 | 2005 | 50.756277388491 | 2004 | 50.654092769934 | 2003 | 50.545806442255 | 2002 | 50.431540811127 | 2001 | 50.314168266582 | 2000 | 50.22290516096 | 1999 | 50.160411573157 | 1998 | 50.093600501444 | 1997 | 50.021120245119 | 1996 | 49.949564759318 | 1995 | 49.878229061615 | 1994 | 49.810967777468 | 1993 | 49.750361993202 | 1992 | 49.687720875599 | 1991 | 49.616216624649 | 1990 | 49.541533544283 | 1989 | 49.460615664861 | 1988 | 49.379732696401 | 1987 | 49.309901850707 | 1986 | 49.246240117122 | 1985 | 49.187395889895 | 1984 | 49.130346004937 | 1983 | 49.075591300846 | 1982 | 49.022514966073 | 1981 | 48.968735800798 | 1980 | 48.913026239582 | 1979 | 48.855401427769 | 1978 | 48.800012431654 | 1977 | 48.745057225583 | 1976 | 48.686299304753 | 1975 | 48.625365982689 | 1974 | 48.562475537096 | 1973 | 48.4980148047 | 1972 | 48.431745910804 | 1971 | 48.363988860696 | 1970 | 48.290939963446 | 1969 | 48.205802574376 | 1968 | 48.112036863917 | 1967 | 48.014416721516 | 1966 | 47.914678601357 | 1965 | 47.813592184445 | 1964 | 47.709986721843 | 1963 | 47.604052700201 | 1962 | 47.495443440663 | 1961 | 47.382431091717 | 1960 | 47.263276467975 |
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