| Year | Value | | 2024 | 49.853395529086 | | 2023 | 49.864729969469 | | 2022 | 49.87857116901 | | 2021 | 49.895872923665 | | 2020 | 49.912460963588 | | 2019 | 49.92990750588 | | 2018 | 49.952464386244 | | 2017 | 49.977420685642 | | 2016 | 50.004526476296 | | 2015 | 50.034817455045 | | 2014 | 50.067611042354 | | 2013 | 50.102933708749 | | 2012 | 50.140113296678 | | 2011 | 50.176690768023 | | 2010 | 50.212973044916 | | 2009 | 50.250493641938 | | 2008 | 50.289603927673 | | 2007 | 50.332461503943 | | 2006 | 50.378822998371 | | 2005 | 50.402562595959 | | 2004 | 50.424035999091 | | 2003 | 50.467650296579 | | 2002 | 50.510590552238 | | 2001 | 50.552783148589 | | 2000 | 50.595122783409 | | 1999 | 50.638050373157 | | 1998 | 50.682415127265 | | 1997 | 50.731062306283 | | 1996 | 50.781979199162 | | 1995 | 50.828920667081 | | 1994 | 50.868399046929 | | 1993 | 50.920938320427 | | 1992 | 50.97840932899 | | 1991 | 51.020437013063 | | 1990 | 51.061151620597 | | 1989 | 51.100151552485 | | 1988 | 51.13857718618 | | 1987 | 51.177070972085 | | 1986 | 51.214757176895 | | 1985 | 51.252068086202 | | 1984 | 51.290453197467 | | 1983 | 51.330341030031 | | 1982 | 51.372384669478 | | 1981 | 51.417152926424 | | 1980 | 51.464097455169 | | 1979 | 51.512100998081 | | 1978 | 51.560186697971 | | 1977 | 51.608963563169 | | 1976 | 51.660312264576 | | 1975 | 51.715515757645 |
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