| Year | Value | | 2024 | 49.343432168078 | | 2023 | 49.352812061517 | | 2022 | 49.359004277962 | | 2021 | 49.3557511799 | | 2020 | 49.343740420436 | | 2019 | 49.327534800086 | | 2018 | 49.303861719148 | | 2017 | 49.284043801622 | | 2016 | 49.274256665029 | | 2015 | 49.264345094939 | | 2014 | 49.265315499333 | | 2013 | 49.277145474806 | | 2012 | 49.291067023516 | | 2011 | 49.311306930523 | | 2010 | 49.333565370046 | | 2009 | 49.359344050382 | | 2008 | 49.387854965094 | | 2007 | 49.415110122583 | | 2006 | 49.441147934667 | | 2005 | 49.466621120544 | | 2004 | 49.489763983228 | | 2003 | 49.510141039635 | | 2002 | 49.53209216415 | | 2001 | 49.555548073491 | | 2000 | 49.579484778468 | | 1999 | 49.603251176336 | | 1998 | 49.626716061987 | | 1997 | 49.649945616346 | | 1996 | 49.673425044982 | | 1995 | 49.698235794538 | | 1994 | 49.722818177332 | | 1993 | 49.748585092413 | | 1992 | 49.777957814987 | | 1991 | 49.808724078064 | | 1990 | 49.842455940479 | | 1989 | 49.879102142789 | | 1988 | 49.916981007656 | | 1987 | 49.955298789134 | | 1986 | 49.974976976802 | | 1985 | 49.99523303309 | | 1984 | 50.036719100109 | | 1983 | 50.079503844043 | | 1982 | 50.123645067326 | | 1981 | 50.16886146944 | | 1980 | 50.213567406102 | | 1979 | 50.257312454617 | | 1978 | 50.29851277969 | | 1977 | 50.336450660032 | | 1976 | 50.372293407782 | | 1975 | 50.405232714968 |
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