| Year | Value | | 2022 | 0.89839522061061 | | 2021 | 0.53477228187492 | | 2020 | 0.58875732404306 | | 2019 | 0.67506137324564 | | 2018 | 0.660090844249 | | 2017 | 0.80767318188495 | | 2016 | 0.88096981535992 | | 2015 | 0.99508473695841 | | 2014 | 1.1277366773493 | | 2013 | 1.2091415893014 | | 2012 | 1.3134409886898 | | 2011 | 1.297189390693 | | 2010 | 1.2456661795621 | | 2009 | 1.2611272893768 | | 2008 | 1.2463330153517 | | 2007 | 1.0347345152783 | | 2006 | 0.80539273916098 | | 2005 | 0.68107296418737 | | 2004 | 0.59093093969025 | | 2003 | 0.58653269198689 | | 2002 | 0.53929080505049 | | 2001 | 0.50604691055724 | | 2000 | 0.64904482119267 | | 1999 | 0.6847594334127 | | 1998 | 0.59541034334665 | | 1997 | 0.54221993602931 | | 1996 | 0.50688168276214 | | 1995 | 0.51912551981252 | | 1994 | 0.56938822776503 | | 1993 | 0.5952293301816 | | 1992 | 0.57718026812669 | | 1991 | 0.47650358500492 | | 1990 | 0.34415141283521 | | 1989 | 0.41280753478562 | | 1988 | 0.53792275933923 | | 1987 | 0.4680495467528 | | 1986 | 0.35668864373097 | | 1985 | 0.29947150036425 | | 1984 | 0.28220267282876 | | 1983 | 0.33106029240603 | | 1982 | 0.367278280054 | | 1981 | 0.34407965607606 | | 1980 | 0.32122557557038 | | 1979 | 0.34056557006731 | | 1978 | 0.38178858294931 | | 1977 | 0.42266131952256 | | 1976 | 0.46901391950002 | | 1975 | 0.55188889731444 | | 1974 | 0.62034941518839 | | 1973 | 0.69950482955189 | | 1972 | 0.76480300223372 | | 1971 | 0.70129338139391 | | 1970 | 0.7265160194964 | | 1969 | 0.81472824860547 | | 1968 | 0.84060210609835 | | 1967 | 0.83653653164001 | | 1966 | 0.79837988180613 | | 1965 | 0.77732707668089 | | 1964 | 0.7554028136359 | | 1963 | 0.75612351555472 | | 1962 | 0.80340155650308 | | 1961 | 0.79435392250443 |
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