| Year | Value | | 2022 | 44.959285645695 | | 2021 | 45.020053930993 | | 2020 | 45.106515236626 | | 2019 | 45.194855566294 | | 2018 | 45.301222573705 | | 2017 | 45.408799606441 | | 2016 | 45.514413774694 | | 2015 | 45.617045815754 | | 2014 | 45.715605568301 | | 2013 | 45.812327560803 | | 2012 | 45.905618989158 | | 2011 | 46.008297780521 | | 2010 | 46.128168515487 | | 2009 | 46.252128667313 | | 2008 | 46.376592509069 | | 2007 | 46.498344257892 | | 2006 | 46.618950162003 | | 2005 | 46.735183178516 | | 2004 | 46.838174734037 | | 2003 | 46.938233560369 | | 2002 | 47.047716339612 | | 2001 | 47.143195006404 | | 2000 | 47.223674879431 | | 1999 | 47.305234199306 | | 1998 | 47.381339587416 | | 1997 | 47.450432809259 | | 1996 | 47.521141908601 | | 1995 | 47.595478728367 | | 1994 | 47.736188585099 | | 1993 | 47.953446412266 | | 1992 | 48.238340157026 | | 1991 | 48.383624532187 | | 1990 | 48.33822994771 | | 1989 | 48.265029786676 | | 1988 | 48.212269197389 | | 1987 | 48.216397860692 | | 1986 | 48.234481912922 | | 1985 | 48.252898606924 | | 1984 | 48.261392829441 | | 1983 | 48.25888099618 | | 1982 | 48.250396391518 | | 1981 | 48.243334019387 | | 1980 | 48.236480673964 | | 1979 | 48.188829527894 | | 1978 | 48.169094839617 | | 1977 | 48.220061014533 | | 1976 | 48.26384321297 | | 1975 | 48.329516977192 | | 1974 | 48.427942012815 | | 1973 | 48.529140122918 | | 1972 | 48.631709092887 | | 1971 | 48.733057678673 | | 1970 | 48.780587892015 | | 1969 | 48.776086181365 | | 1968 | 48.772523123692 | | 1967 | 48.763983994886 | | 1966 | 48.748767150977 | | 1965 | 48.73031099111 | | 1964 | 48.70741017278 | | 1963 | 48.67644251907 | | 1962 | 48.641182026002 | | 1961 | 48.603064624936 | | 1960 | 48.558725477221 |
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