| Year | Value | | 2022 | 0.42705656262948 | | 2021 | 0.8159774106784 | | 2020 | 0.26176127285265 | | 2019 | 0.72956717301874 | | 2018 | 1.1378102584923 | | 2017 | 1.5923404255319 | | 2016 | 1.7419849185113 | | 2015 | 1.8863087786068 | | 2014 | 1.8877891173906 | | 2013 | 1.8682239564238 | | 2012 | 1.8594998831503 | | 2011 | 1.407162104666 | | 2010 | 0.81625145324697 | | 2006 | 1.9862424763543 | | 2005 | 1.4525757240769 | | 2004 | 2.7057580559958 | | 2003 | 2.0346772508878 | | 2002 | 6.3064741499767 | | 2001 | 2.5498043400925 | | 2000 | 3.0537918871252 | | 1999 | 2.2380830996686 | | 1997 | 2.998266897747 | | 1996 | 2.8827715726006 | | 1995 | 3.181653152608 | | 1994 | 3.1147129036311 | | 1993 | 3.300303871053 | | 1992 | 3.8027717182086 | | 1991 | 3.9793650793651 | | 1990 | 4.103903785489 | | 1989 | 4.9310307374823 | | 1988 | 5.2087065567897 | | 1987 | 5.8238889218537 | | 1986 | 5.5038198632891 | | 1985 | 5.4866691501251 | | 1984 | 5.677649911053 | | 1983 | 5.5608505815226 | | 1982 | 5.1225452884762 | | 1981 | 4.8643183463564 | | 1980 | 6.6290856278728 | | 1979 | 8.5205214872043 | | 1978 | 7.9913135398474 | | 1977 | 6.5381266611676 | | 1976 | 4.6267135976287 | | 1975 | 3.3994463889461 | | 1974 | 2.9769976394958 | | 1973 | 2.6258536290566 | | 1972 | 2.1828434850805 | | 1971 | 2.2880616881627 | | 1970 | 2.4387007748647 | | 1969 | 2.4227688787185 | | 1968 | 2.0681265206813 | | 1967 | 1.3600572655691 | | 1966 | 1.3224623546852 | | 1965 | 1.189568400183 |
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