| Year | Value | | 2024 | 50.656567831922 | | 2023 | 50.647187938483 | | 2022 | 50.640995722038 | | 2021 | 50.6442488201 | | 2020 | 50.656259579564 | | 2019 | 50.672465199914 | | 2018 | 50.696138280852 | | 2017 | 50.715956198378 | | 2016 | 50.725743334971 | | 2015 | 50.735654905061 | | 2014 | 50.734684500667 | | 2013 | 50.722854525194 | | 2012 | 50.708932976484 | | 2011 | 50.688693069477 | | 2010 | 50.666434629954 | | 2009 | 50.640655949618 | | 2008 | 50.612145034906 | | 2007 | 50.584889877417 | | 2006 | 50.558852065333 | | 2005 | 50.533378879456 | | 2004 | 50.510236016772 | | 2003 | 50.489858960365 | | 2002 | 50.46790783585 | | 2001 | 50.444451926509 | | 2000 | 50.420515221532 | | 1999 | 50.396748823664 | | 1998 | 50.373283938013 | | 1997 | 50.350054383654 | | 1996 | 50.326574955018 | | 1995 | 50.301764205462 | | 1994 | 50.277181822668 | | 1993 | 50.251414907587 | | 1992 | 50.222042185013 | | 1991 | 50.191275921936 | | 1990 | 50.157544059521 | | 1989 | 50.120897857211 | | 1988 | 50.083018992344 | | 1987 | 50.044701210866 | | 1986 | 50.025023023198 | | 1985 | 50.00476696691 | | 1984 | 49.963280899891 | | 1983 | 49.920496155957 | | 1982 | 49.876354932674 | | 1981 | 49.83113853056 | | 1980 | 49.786432593898 | | 1979 | 49.742687545383 | | 1978 | 49.70148722031 | | 1977 | 49.663549339968 | | 1976 | 49.627706592218 | | 1975 | 49.594767285032 |
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