| Year | Value | | 2022 | 1.7463287294597 | | 2021 | 0.73738372145228 | | 2020 | 0.94074215338185 | | 2019 | 1.8395450496903 | | 2018 | 2.2720598723016 | | 2017 | 2.8227580554717 | | 2016 | 3.6232143176414 | | 2015 | 4.0596104113565 | | 2014 | 5.7666007457914 | | 2013 | 5.7364002371961 | | 2012 | 4.5156029139938 | | 2011 | 9.8844641982388 | | 2010 | 2.5032760584424 | | 2009 | 3.3464542014201 | | 2008 | 14.006810770252 | | 2007 | 8.7056092357887 | | 2006 | 4.2823960480256 | | 2005 | 5.3932310689066 | | 2004 | 4.4373808010172 | | 2003 | 3.3372749967153 | | 2002 | 0.92825885161107 | | 2001 | 1.5896537787957 | | 2000 | 4.608229988726 | | 1999 | 2.159516268356 | | 1998 | 7.6732289567508 | | 1997 | 4.7084443602819 | | 1996 | 12.425486618005 | | 1995 | 10.193206763074 | | 1994 | 7.8740442146743 | | 1993 | 8.52787695688 | | 1992 | 12.060323601829 | | 1991 | 21.447069817114 | | 1990 | 17.118774604824 | | 1989 | 15.173468112573 | | 1988 | 16.002091054939 | | 1987 | 14.578698448919 | | 1986 | 276.3359675632 | | 1985 | 11,749.639632144 | | 1984 | 1,281.3499417449 | | 1983 | 275.58628356036 | | 1982 | 123.53571856533 | | 1981 | 32.133601113342 | | 1980 | 47.241650101843 | | 1979 | 19.7197167788 | | 1978 | 10.355672275719 | | 1977 | 8.1072555205042 | | 1976 | 4.4940116470722 | | 1975 | 7.9767460254687 | | 1974 | 62.836075602924 | | 1973 | 31.486028789162 | | 1972 | 6.5115440115437 | | 1971 | 3.6746143057503 | | 1970 | 3.9555092109977 | | 1969 | 2.2097484725132 | | 1968 | 5.470623501623 | | 1967 | 11.199999999 | | 1966 | 6.951871657754 | | 1965 | 2.8602860286027 | | 1964 | 10.181818181818 | | 1963 | 0.70635721455239 | | 1962 | 5.879331422253 | | 1961 | 7.561493071839 | | 1960 | 11.533152575619 |
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