| Year | Value | | 2022 | 1.0625570973844 | | 2021 | 1.2062178802275 | | 2020 | 1.2678408731027 | | 2019 | 1.2516781219317 | | 2018 | 1.2544131320454 | | 2017 | 1.2397919001165 | | 2016 | 1.1895336224405 | | 2015 | 1.1049143879943 | | 2014 | 1.021936221937 | | 2013 | 0.93110853556566 | | 2012 | 0.83281787289949 | | 2011 | 0.73539449501346 | | 2010 | 0.67352848270633 | | 2009 | 0.70701358871822 | | 2008 | 0.58057526205029 | | 2007 | 0.33760569608704 | | 2006 | 0.032572927734326 | | 2005 | 0.40173587545233 | | 2004 | 0.38437474902057 | | 2003 | 0.22573259882656 | | 2002 | 0.097022604769251 | | 2001 | 0.042169999747009 | | 2000 | 0.21974161288221 | | 1999 | 0.43237530179016 | | 1998 | 0.65989530605573 | | 1997 | 0.89015035747626 | | 1996 | 1.0809075877906 | | 1995 | 1.2191932944884 | | 1994 | 1.3257941579788 | | 1993 | 1.4407892429209 | | 1992 | 1.5725852384516 | | 1991 | 1.6818337468005 | | 1990 | 1.7894595645369 | | 1989 | 1.9057804464953 | | 1988 | 2.0272948690957 | | 1987 | 2.3311042774889 | | 1986 | 2.6307716805871 | | 1985 | 2.7230829968255 | | 1984 | 2.7670297148074 | | 1983 | 2.7783006247828 | | 1982 | 2.7862424316641 | | 1981 | 2.790134525879 | | 1980 | 2.7917359779686 | | 1979 | 2.7929359610461 | | 1978 | 2.8016250150589 | | 1977 | 2.976173761675 | | 1976 | 3.2597769989833 | | 1975 | 3.4132658056678 | | 1974 | 3.4393697259699 | | 1973 | 3.4388684983606 | | 1972 | 3.4645007940103 | | 1971 | 3.4945188469798 | | 1970 | 3.5374252934444 | | 1969 | 3.5984079167339 | | 1968 | 3.6404176954738 | | 1967 | 3.4409659214657 | | 1966 | 3.1604502419793 | | 1965 | 3.06970075856 | | 1964 | 3.0521679425265 | | 1963 | 3.0692217710141 | | 1962 | 3.0781893770064 | | 1961 | 3.077108368614 |
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