| Year | Value | | 2022 | 0.6914815713035 | | 2021 | 1.1438209158096 | | 2020 | 1.4701020316018 | | 2019 | 1.8307469424654 | | 2018 | 1.895586750575 | | 2017 | 1.5122896059229 | | 2016 | 1.068611890834 | | 2015 | 0.94199406710663 | | 2014 | 0.94713692337595 | | 2013 | 0.99003478145496 | | 2012 | 1.0396649999409 | | 2011 | 1.0935830743658 | | 2010 | 1.126884715439 | | 2009 | 1.1315413059527 | | 2008 | 1.167873546047 | | 2007 | 1.2399674425138 | | 2006 | 1.2988651766919 | | 2005 | 1.3656523387696 | | 2004 | 1.4281705307049 | | 2003 | 1.4811315705424 | | 2002 | 1.5348669161418 | | 2001 | 1.5755323721494 | | 2000 | 1.6198314055116 | | 1999 | 1.6742155832136 | | 1998 | 1.7344920930048 | | 1997 | 1.7839561107605 | | 1996 | 1.8249751694985 | | 1995 | 1.8933693496789 | | 1994 | 1.9474913642204 | | 1993 | 1.9713513727806 | | 1992 | 1.9830867740273 | | 1991 | 2.0380059470879 | | 1990 | 2.1024599331048 | | 1989 | 2.109580117362 | | 1988 | 2.11350051755 | | 1987 | 2.1233082036055 | | 1986 | 2.1383169436472 | | 1985 | 2.1968470923432 | | 1984 | 2.2799770813467 | | 1983 | 2.2982561158307 | | 1982 | 2.2853866501334 | | 1981 | 2.3028281007157 | | 1980 | 2.3066080153304 | | 1979 | 2.2764195356341 | | 1978 | 2.2638374754754 | | 1977 | 2.1959431949909 | | 1976 | 2.1526873652222 | | 1975 | 2.1851517292232 | | 1974 | 2.2147366456011 | | 1973 | 2.2498750256965 | | 1972 | 2.275398612486 | | 1971 | 2.3643319030102 | | 1970 | 2.4844901694571 | | 1969 | 2.5818595815941 | | 1968 | 2.6956739686132 | | 1967 | 2.7916836587903 | | 1966 | 2.8884894785914 | | 1965 | 2.9770436549575 | | 1964 | 3.0261952037966 | | 1963 | 3.0659610593645 | | 1962 | 3.0961450145784 | | 1961 | 3.1048896156647 |
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