| Year | Value | | 2021 | 1.2000396707329 | | 2020 | 1.2000396707329 | | 2019 | 1.2000396707329 | | 2018 | 1.2000396707329 | | 2017 | 1.2069825436409 | | 2016 | 1.2069825436409 | | 2015 | 1.2069825436409 | | 2014 | 1.2089775561097 | | 2013 | 1.2089775561097 | | 2012 | 1.2089775561097 | | 2011 | 1.2189526184539 | | 2010 | 1.2269326683292 | | 2009 | 1.2369077306733 | | 2008 | 1.2468827930175 | | 2007 | 1.2468827930175 | | 2006 | 1.286783042394 | | 2005 | 1.286783042394 | | 2004 | 1.286783042394 | | 2003 | 1.286783042394 | | 2002 | 1.286783042394 | | 2001 | 1.286783042394 | | 2000 | 1.286783042394 | | 1999 | 1.286783042394 | | 1998 | 1.2967581047382 | | 1997 | 1.3266832917706 | | 1996 | 1.3366583541147 | | 1995 | 1.3466334164589 | | 1994 | 1.3466334164589 | | 1993 | 1.3466334164589 | | 1992 | 1.356608478803 | | 1991 | 1.356608478803 | | 1990 | 1.356608478803 | | 1989 | 1.3466334164589 | | 1988 | 1.3466334164589 | | 1987 | 1.3466334164589 | | 1986 | 1.3466334164589 | | 1985 | 1.3366583541147 | | 1984 | 1.3366583541147 | | 1983 | 1.3366583541147 | | 1982 | 1.3366583541147 | | 1981 | 1.3266832917706 | | 1980 | 1.3266832917706 | | 1979 | 1.3067331670823 | | 1978 | 1.2967581047382 | | 1977 | 1.286783042394 | | 1976 | 1.2668329177057 | | 1975 | 1.2568578553616 | | 1974 | 1.2468827930175 | | 1973 | 1.2369077306733 | | 1972 | 1.2269326683292 | | 1971 | 1.216957605985 | | 1970 | 1.2069825436409 | | 1969 | 1.1970074812968 | | 1968 | 1.1970074812968 | | 1967 | 1.1970074812968 | | 1966 | 1.1970074812968 | | 1965 | 1.1970074812968 | | 1964 | 1.1970074812968 | | 1963 | 1.1970074812968 | | 1962 | 1.1970074812968 | | 1961 | 1.1970074812968 |
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