| Year | Value | | 2024 | 48.130008974453 | | 2023 | 48.120514370587 | | 2022 | 48.112740950918 | | 2021 | 48.119897325495 | | 2020 | 48.147496274267 | | 2019 | 48.171635873768 | | 2018 | 48.177799718737 | | 2017 | 48.180251018766 | | 2016 | 48.181812356628 | | 2015 | 48.176532769556 | | 2014 | 48.166860951319 | | 2013 | 48.152962004286 | | 2012 | 48.136187138934 | | 2011 | 48.115500847179 | | 2010 | 48.084602144005 | | 2009 | 48.039965972949 | | 2008 | 47.986157747948 | | 2007 | 47.928251375956 | | 2006 | 47.869519192391 | | 2005 | 47.806564456172 | | 2004 | 47.736105391217 | | 2003 | 47.727835923726 | | 2002 | 47.802027877797 | | 2001 | 47.896812252559 | | 2000 | 47.99540834508 | | 1999 | 48.091782374744 | | 1998 | 48.182750082796 | | 1997 | 48.266783261488 | | 1996 | 48.342923081787 | | 1995 | 48.411574646013 | | 1994 | 48.473513918568 | | 1993 | 48.530566041341 | | 1992 | 48.581834446184 | | 1991 | 48.622746808647 | | 1990 | 48.645198929245 | | 1989 | 48.65171471032 | | 1988 | 48.648595791285 | | 1987 | 48.635953914483 | | 1986 | 48.61839665785 | | 1985 | 48.597595025013 | | 1984 | 48.57325638736 | | 1983 | 48.543692573142 | | 1982 | 48.506895721065 | | 1981 | 48.462811150213 | | 1980 | 48.410622071749 | | 1979 | 48.354176345527 | | 1978 | 48.301006423535 | | 1977 | 48.243333397877 | | 1976 | 48.173577662051 | | 1975 | 48.09422956116 |
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