| Year | Value | | 2024 | 49.335036949273 | | 2023 | 49.355481445392 | | 2022 | 49.380053201589 | | 2021 | 49.429814403091 | | 2020 | 49.482125340887 | | 2019 | 49.512481024911 | | 2018 | 49.540313866864 | | 2017 | 49.567272048677 | | 2016 | 49.591975154836 | | 2015 | 49.610875822966 | | 2014 | 49.625103315891 | | 2013 | 49.636489738867 | | 2012 | 49.645449176891 | | 2011 | 49.672589766502 | | 2010 | 49.71858591647 | | 2009 | 49.764624532525 | | 2008 | 49.811180929956 | | 2007 | 49.85832273216 | | 2006 | 49.906539404445 | | 2005 | 49.955249937092 | | 2004 | 50.002731619051 | | 2003 | 50.047915211041 | | 2002 | 50.097119916503 | | 2001 | 50.155445036006 | | 2000 | 50.219410035494 | | 1999 | 50.285371600843 | | 1998 | 50.349329429773 | | 1997 | 50.40825849655 | | 1996 | 50.46283934581 | | 1995 | 50.51666937901 | | 1994 | 50.571751554425 | | 1993 | 50.605989411893 | | 1992 | 50.617645308156 | | 1991 | 50.628575821862 | | 1990 | 50.639839974401 | | 1989 | 50.652510342731 | | 1988 | 50.667020685669 | | 1987 | 50.684781469716 | | 1986 | 50.704341666108 | | 1985 | 50.724045970023 | | 1984 | 50.746403933806 | | 1983 | 50.772728369166 | | 1982 | 50.803728154243 | | 1981 | 50.838352292341 | | 1980 | 50.853714855465 | | 1979 | 50.846215174372 | | 1978 | 50.834510487613 | | 1977 | 50.819800921185 | | 1976 | 50.805297786849 | | 1975 | 50.79270223633 |
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