| Year | Value | | 2024 | 46.140370705244 | | 2023 | 46.099170756473 | | 2022 | 46.061152091897 | | 2021 | 46.010234493618 | | 2020 | 45.953237410072 | | 2019 | 45.982694684796 | | 2018 | 46.121028404626 | | 2017 | 46.260947675724 | | 2016 | 46.386828500787 | | 2015 | 46.533483398987 | | 2014 | 46.788214043802 | | 2013 | 47.093155031732 | | 2012 | 47.16577540107 | | 2011 | 47.015544614704 | | 2010 | 46.879756468798 | | 2009 | 46.766435061464 | | 2008 | 46.6621074228 | | 2007 | 46.554761164646 | | 2006 | 46.429847394478 | | 2005 | 46.281158542739 | | 2004 | 46.082437818475 | | 2003 | 45.87995930824 | | 2002 | 45.705788852997 | | 2001 | 45.540512608516 | | 2000 | 45.437480446345 | | 1999 | 45.53727316015 | | 1998 | 45.789246383071 | | 1997 | 46.045946542964 | | 1996 | 46.301121558854 | | 1995 | 46.417354891241 | | 1994 | 46.398330351819 | | 1993 | 46.365746396286 | | 1992 | 46.319344549378 | | 1991 | 46.266171384655 | | 1990 | 46.192161489055 | | 1989 | 46.21612579458 | | 1988 | 46.346626604753 | | 1987 | 46.490860890191 | | 1986 | 46.655733029093 | | 1985 | 46.884359704873 | | 1984 | 47.165566886623 | | 1983 | 47.424265723512 | | 1982 | 47.707578383488 | | 1981 | 47.968069666183 | | 1980 | 48.129736777769 | | 1979 | 48.131636540488 | | 1978 | 48.046623794212 | | 1977 | 47.980201181542 | | 1976 | 47.9482498611 | | 1975 | 47.897897897898 |
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