| Year | Value | | 2022 | 0.66107817570116 | | 2021 | 0.68338276890154 | | 2020 | 0.81190393111558 | | 2019 | 0.88607377998981 | | 2018 | 0.92001607012489 | | 2017 | 0.97642629715016 | | 2016 | 1.0103735011334 | | 2015 | 1.0313612661854 | | 2014 | 1.0522623239154 | | 2013 | 1.0799569075198 | | 2012 | 1.1132286461926 | | 2011 | 1.1269214730403 | | 2010 | 1.052922954774 | | 2009 | 1.1020213912832 | | 2008 | 1.1253104521902 | | 2007 | 1.1621980279477 | | 2006 | 1.2006668497182 | | 2005 | 1.2442122910155 | | 2004 | 1.2746555833349 | | 2003 | 1.3137794372012 | | 2002 | 1.3708017184372 | | 2001 | 1.420947029105 | | 2000 | 1.4729466124962 | | 1999 | 1.5224670229515 | | 1998 | 1.5678831171252 | | 1997 | 1.6102907620013 | | 1996 | 1.6529655340151 | | 1995 | 1.7021299700107 | | 1994 | 1.7419108683453 | | 1993 | 1.7752935906206 | | 1992 | 1.8140453267027 | | 1991 | 1.868241209901 | | 1990 | 1.8929287882071 | | 1989 | 1.8981575308341 | | 1988 | 1.9302167557275 | | 1987 | 1.9565226378914 | | 1986 | 1.9955854096988 | | 1985 | 2.0407082153564 | | 1984 | 2.0865591340093 | | 1983 | 2.1209546156637 | | 1982 | 2.1305522411951 | | 1981 | 2.177364312381 | | 1980 | 2.2630983189017 | | 1979 | 2.3162319326498 | | 1978 | 2.3462268543797 | | 1977 | 2.3419358127039 | | 1976 | 2.3455550380125 | | 1975 | 2.3793839058022 | | 1974 | 2.4124541787614 | | 1973 | 2.4360670795783 | | 1972 | 2.4528354189435 | | 1971 | 2.4753049394684 | | 1970 | 2.5041361376134 | | 1969 | 2.5421855300718 | | 1968 | 2.586700252881 | | 1967 | 2.6352580178396 | | 1966 | 2.6911353074468 | | 1965 | 2.7441662907335 | | 1964 | 2.7775528403269 | | 1963 | 2.8015143766663 | | 1962 | 2.8112731220966 | | 1961 | 2.8118609840881 |
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