| Year | Value | | 2022 | 5.8283863851796 | | 2021 | 2.0592274691546 | | 2020 | 0.59898633082464 | | 2019 | 1.0005429302724 | | 2018 | 1.0185693018882 | | 2017 | 1.8803844018353 | | 2016 | 3.0706674246402 | | 2015 | 4.6612159809826 | | 2014 | 5.6844181459566 | | 2013 | 5.1998174046561 | | 2012 | 9.2602813706829 | | 2011 | 5.1071328926456 | | 2010 | 10.549200317999 | | 2009 | 6.9780872525155 | | 2008 | 12.030344547718 | | 2007 | 7.894388347573 | | 2006 | 8.3296035146535 | | 2005 | 6.8745345958352 | | 2004 | 3.7215493899596 | | 2003 | 3.8111062439687 | | 2002 | 4.1500586166472 | | 2001 | 5.536653263223 | | 2000 | 3.5554131966688 | | 1999 | 3.43913590882 | | 1998 | 5.612709076912 | | 1997 | 3.6260787584308 | | 1996 | 3.4045744281962 | | 1995 | 5.1822053951727 | | 1994 | 8.8146940176811 | | 1993 | 10.835235920852 | | 1992 | 6.4398541919806 | | 1991 | 3.7831021437579 | | 1990 | 11.064425770308 | | 1989 | 11.432131813357 | | 1988 | 7.7584920674392 | | 1987 | 10.751858992074 | | 1986 | 7.6936765932314 | | 1985 | 7.622574055202 | | 1984 | 13.334780406632 | | 1983 | 15.174999999333 | | 1982 | 11.634762943167 | | 1981 | 14.331886600939 | | 1980 | 17.470304279577 | | 1979 | 14.722170368999 | | 1978 | 10.256586168874 | | 1977 | 11.744863539094 | | 1976 | 10.692464357773 | | 1975 | 16.979060465689 | | 1974 | 22.024977271762 | | 1973 | 14.810745481571 | | 1972 | 9.3010688125333 | | 1971 | 3.53102076329 | | 1970 | 2.5239005736269 | | 1969 | 2.4352027160153 | | 1968 | 8.2320520069128 | | 1967 | 2.1362586601549 | | 1966 | 4.0943580499049 | | 1965 | 1.7816179844885 | | 1964 | 0.86379762440665 | | 1963 | 3.7612035849165 | | 1962 | 2.9833525633929 | | 1961 | 1.5227576978899 | | 1960 | 2.0800000000782 |
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