| Year | Value | | 2022 | 4.2094638340217 | | 2021 | 1.5601299052567 | | 2020 | 1.9209680056685 | | 2019 | 3.0305866496949 | | 2018 | 3.1983464156241 | | 2017 | 3.8087980695316 | | 2016 | 3.5258051568793 | | 2015 | 6.3631211311561 | | 2014 | 6.3949254081992 | | 2013 | 6.4125133015642 | | 2012 | 4.2794999964197 | | 2011 | 5.3560477898215 | | 2010 | 5.1342040076793 | | 2009 | 4.3864155501473 | | 2008 | 10.226664547315 | | 2007 | 6.406562813257 | | 2006 | 13.10867209853 | | 2005 | 10.453198419386 | | 2004 | 6.0640598852652 | | 2003 | 6.7573171936285 | | 2002 | 11.900117566378 | | 2001 | 11.500114879177 | | 2000 | 3.6886191595835 | | 1999 | 20.47783111264 | | 1998 | 58.451044472395 | | 1997 | 6.2261416338759 | | 1996 | 7.9732808561142 | | 1995 | 9.4203232164461 | | 1994 | 8.5320052541885 | | 1993 | 9.6718933818012 | | 1992 | 7.5235171702275 | | 1991 | 9.4190582772415 | | 1990 | 7.8191914473055 | | 1989 | 6.4155396349497 | | 1988 | 8.045367151231 | | 1987 | 9.2786561316159 | | 1986 | 5.822666961752 | | 1985 | 4.7245361568021 | | 1984 | 10.45503482319 | | 1983 | 11.799740521518 | | 1982 | 9.4454239535345 | | 1981 | 12.265908514191 | | 1980 | 18.035430161689 | | 1979 | 16.232765755018 | | 1978 | 8.1125825952592 | | 1977 | 11.052089794625 | | 1976 | 19.828653695664 | | 1975 | 19.165697133559 | | 1974 | 40.491790438471 | | 1973 | 31.041881271113 | | 1972 | 6.5217492128302 | | 1971 | 4.2337489448834 | | 1970 | 12.399464648781 | | 1969 | 15.479870215162 | | 1968 | 128.8430420712 | | 1967 | 106 | | 1966 | 1,136.2541122077 | | 1965 | 306.76311030741 | | 1964 | 108.99470899471 | | 1963 | 145.91078066914 | | 1962 | 131.39784946237 | | 1961 | 13.691931540342 | | 1960 | 39.590443686007 |
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