| Year | Value | | 2022 | 6.1210600403942 | | 2021 | 2.3048595904048 | | 2020 | 0.18191666666663 | | 2019 | 0.56526056878033 | | 2018 | 0.43862011844684 | | 2017 | 0.57626031016635 | | 2016 | 0.53226873971625 | | 2015 | 0.5226181670753 | | 2014 | 1.0251480303939 | | 2013 | 2.3586041539983 | | 2012 | 4.5756027037653 | | 2011 | 5.2477933984048 | | 2010 | 2.8236613488561 | | 2009 | 0.59672025742494 | | 2008 | 6.6277817735213 | | 2007 | 2.1048800363321 | | 2006 | 0.96290177816511 | | 2005 | 0.42510627656913 | | 2004 | 1.6627271986307 | | 2003 | 0.50790530023754 | | 2002 | 0.39167686658506 | | 2001 | 0.99719795615596 | | 2000 | 1.3616239244845 | | 1999 | 0.01670983373708 | | 1998 | 0.26750229287614 | | 1997 | 2.0035861853896 | | 1996 | 1.3831805248188 | | 1995 | 1.7205338478852 | | 1994 | 3.100132625995 | | 1993 | 2.2892996438864 | | 1992 | 2.2630711870285 | | 1991 | 3.4257017307864 | | 1990 | 3.4607533865282 | | 1989 | 2.345456271959 | | 1988 | 1.5231851923263 | | 1987 | 0.52330652194977 | | 1986 | -1.3857033639144 | | 1985 | 0.48012291146536 | | 1984 | 2.6009852216749 | | 1983 | 1.1964107676969 | | 1982 | 3.916286779942 | | 1981 | 8.1820219681685 | | 1980 | 8.5269431942586 | | 1979 | 4.076465375364 | | 1978 | 4.8725438130643 | | 1977 | 3.1639501438158 | | 1976 | -1.8418929819842 | | 1975 | 2.5365315687895 | | 1974 | 22.368421052632 | | 1973 | 19.636730575177 | | 1972 | 2.0807581376187 | | 1971 | 1.7610062893082 | | 1970 | 0.46335299073263 | | 1969 | 0.27305187985694 | | 1968 | 0.65539112050733 | | 1967 | 3.3428009613282 | | 1966 | 2.0057945174949 | | 1965 | 0.17861129716461 | | 1964 | 1.7260958437428 | | 1963 | 2.2051996285983 | | 1962 | 0.41958041958031 | | 1961 | 0.40000000000007 |
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