| Year | Value | | 2022 | 0.90389201395394 | | 2021 | 0.49197376876991 | | 2020 | 0.52168578635416 | | 2019 | 0.57994953683624 | | 2018 | 0.64585096268581 | | 2017 | 0.67531071571693 | | 2016 | 0.6835672103958 | | 2015 | 0.70541465068261 | | 2014 | 0.76840775619091 | | 2013 | 0.80641719372353 | | 2012 | 0.86836150707789 | | 2011 | 1.0907064741525 | | 2010 | 1.1539425270682 | | 2009 | 1.2046015780281 | | 2008 | 1.5158479636831 | | 2007 | 1.8962773298254 | | 2006 | 2.3071493240444 | | 2005 | 2.8122183749941 | | 2004 | 3.0726504065443 | | 2003 | 3.2388427344242 | | 2002 | 3.7193880990357 | | 2001 | 4.3490207775311 | | 2000 | 7.6138439057773 | | 1999 | 9.5069426825902 | | 1998 | 7.2769361489553 | | 1997 | 3.3431774775412 | | 1996 | 2.1171384891138 | | 1995 | 2.2256160543013 | | 1994 | 2.8684387023898 | | 1993 | 3.071688350643 | | 1992 | 3.4417083493651 | | 1991 | 5.7051315446731 | | 1990 | 9.6579698086295 | | 1989 | 10.276648456359 | | 1988 | 8.5014361098123 | | 1987 | 6.855673684942 | | 1986 | 6.6972375690608 | | 1985 | 6.8239041989714 | | 1984 | 7.9691481616309 | | 1983 | 7.1796178343949 | | 1982 | 7.5390184279804 | | 1981 | 7.5369580315507 | | 1980 | 8.7085821332397 | | 1979 | 6.8865880086684 | | 1978 | 4.8109024517475 | | 1977 | 3.9677808530267 | | 1976 | 4.1317225253313 | | 1975 | 4.4920621150343 | | 1974 | 2.7945823927765 | | 1973 | 1.9255540822125 | | 1972 | 1.9364102564103 | | 1971 | 1.9060715041252 | | 1970 | 1.8831098026388 | | 1969 | 2.0206645532465 | | 1968 | 2.1956163689345 | | 1967 | 2.4862249697621 | | 1966 | 3.1071990840132 | | 1965 | 3.2299352507153 | | 1964 | 2.9215844785772 | | 1963 | 2.4283667621776 | | 1962 | 1.9321903294163 | | 1961 | 1.8558776167472 |
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