| Year | Value | | 2022 | 53.018441514508 | | 2021 | 53.921703654104 | | 2020 | 55.330445774732 | | 2019 | 56.018573042481 | | 2018 | 55.057688861952 | | 2017 | 54.867608433277 | | 2016 | 55.038737512036 | | 2015 | 53.990890427761 | | 2014 | 52.524943011084 | | 2013 | 51.717147008041 | | 2012 | 51.142613301024 | | 2011 | 50.159293281434 | | 2010 | 48.913361667291 | | 2009 | 50.080272036367 | | 2008 | 49.773494542726 | | 2007 | 50.996287744479 | | 2006 | 52.572495472651 | | 2005 | 54.384540899612 | | 2004 | 55.236247905557 | | 2003 | 58.021994312934 | | 2002 | 60.983443246075 | | 2001 | 61.933249011065 | | 2000 | 63.570788279495 | | 1999 | 62.571307590673 | | 1998 | 60.451334731295 | | 1997 | 59.648394739053 | | 1996 | 60.047469666964 | | 1995 | 59.062277996158 | | 1994 | 58.179054133557 | | 1993 | 58.348901470685 | | 1992 | 59.715282869615 | | 1991 | 61.918791549198 | | 1990 | 63.649122967397 | | 1989 | 64.283152271896 | | 1988 | 62.115474038641 | | 1987 | 62.782563440979 | | 1986 | 64.86818162484 | | 1985 | 65.070848953811 | | 1984 | 65.764153334513 | | 1983 | 67.451477415698 | | 1982 | 66.566350471681 | | 1981 | 66.416354420002 | | 1980 | 64.689370704772 | | 1979 | 62.895087646645 | | 1978 | 60.717558688134 | | 1977 | 63.240833387692 | | 1976 | 65.823806457873 | | 1975 | 61.991844839612 | | 1974 | 63.928552625809 | | 1973 | 63.452972567303 | | 1972 | 64.282236267826 | | 1971 | 63.209844568358 | | 1970 | 63.898573062245 | | 1969 | 69.21042566507 | | 1968 | 72.854859761482 | | 1967 | 71.183610210679 | | 1966 | 66.152852274051 | | 1965 | 66.660447560554 | | 1964 | 73.205612796789 | | 1963 | 81.162909388769 | | 1962 | 84.853712321459 | | 1961 | 80.572869788201 | | 1960 | 62.893192252228 |
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