| Year | Value | | 2022 | 47.214138848495 | | 2021 | 47.167153405341 | | 2020 | 47.130679109561 | | 2019 | 47.099795709535 | | 2018 | 47.076238238916 | | 2017 | 47.051613299916 | | 2016 | 47.026895451536 | | 2015 | 47.000110279544 | | 2014 | 46.971290553462 | | 2013 | 46.941673966329 | | 2012 | 46.91781154952 | | 2011 | 46.938522323223 | | 2010 | 46.995892683756 | | 2009 | 47.049545695085 | | 2008 | 47.106068063297 | | 2007 | 47.166434495197 | | 2006 | 47.190963213952 | | 2005 | 47.231432815043 | | 2004 | 47.324096009163 | | 2003 | 47.387632549917 | | 2002 | 47.428425909022 | | 2001 | 47.460468821284 | | 2000 | 47.501131420919 | | 1999 | 47.547082077905 | | 1998 | 47.562529203271 | | 1997 | 47.563969974304 | | 1996 | 47.562145900255 | | 1995 | 47.561092413608 | | 1994 | 47.612324394853 | | 1993 | 47.739000889122 | | 1992 | 47.944608566028 | | 1991 | 48.079880013278 | | 1990 | 48.11245284086 | | 1989 | 48.167523261929 | | 1988 | 48.339964126935 | | 1987 | 48.659992877382 | | 1986 | 48.861365924513 | | 1985 | 48.916548674043 | | 1984 | 48.959959478802 | | 1983 | 49.059626791619 | | 1982 | 49.060842365728 | | 1981 | 48.932422268304 | | 1980 | 47.84299863573 | | 1979 | 46.870076217357 | | 1978 | 47.536052819906 | | 1977 | 48.270599115704 | | 1976 | 48.593462838722 | | 1975 | 48.736731974946 | | 1974 | 48.832478195249 | | 1973 | 48.903568042639 | | 1972 | 48.995597560892 | | 1971 | 49.107034817131 | | 1970 | 49.237677780046 | | 1969 | 49.314524530631 | | 1968 | 49.329079576215 | | 1967 | 49.34696941344 | | 1966 | 49.366670669402 | | 1965 | 49.387394036044 | | 1964 | 49.407887837874 | | 1963 | 49.428126026974 | | 1962 | 49.449154990718 | | 1961 | 49.471720489705 | | 1960 | 49.49612616944 |
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