| Year | Value | | 2022 | 7.4028004869687 | | 2021 | 4.0465260244563 | | 2020 | 0.97529201430706 | | 2019 | 1.8807395496881 | | 2018 | 2.3554044847046 | | 2017 | 1.8634970660947 | | 2016 | 1.3451713763581 | | 2015 | 0.62193424824761 | | 2014 | 1.7644294422934 | | 2013 | 1.2015622767212 | | 2012 | 1.7925077482529 | | 2011 | 3.0344883286728 | | 2010 | 1.7084574916581 | | 2009 | 0.028039731645224 | | 2008 | 3.104685485547 | | 2007 | 2.4955282370849 | | 2006 | 2.6139847480228 | | 2005 | 2.8031494399466 | | 2004 | 2.2672477058321 | | 2003 | 2.5143290934811 | | 2002 | 1.9222130179573 | | 2001 | 2.6756456293266 | | 2000 | 3.0481486142095 | | 1999 | 1.9614350740164 | | 1998 | 1.2741107777008 | | 1997 | 1.9794531590763 | | 1996 | 2.2508676625029 | | 1995 | 2.4770900095576 | | 1994 | 1.3865022530309 | | 1993 | 2.4083681657325 | | 1992 | 2.2594762909476 | | 1991 | 4.9304140252343 | | 1990 | 5.0892166866331 | | 1989 | 4.9053124649745 | | 1988 | 4.0529876280801 | | 1987 | 4.0103359648672 | | 1986 | 3.0464170065995 | | 1985 | 3.7538373463728 | | 1984 | 4.3026568895758 | | 1983 | 4.5380116314672 | | 1982 | 8.4501994499944 | | 1981 | 11.403163877557 | | 1980 | 11.839211241757 | | 1979 | 10.199574054176 | | 1978 | 8.3023435951841 | | 1977 | 7.2390646954371 | | 1976 | 6.6432756326562 | | 1975 | 9.9076677300297 | | 1974 | 11.025987975245 | | 1973 | 6.8327036730862 | | 1972 | 4.1301534887992 | | 1971 | 3.4988423604587 | | 1970 | 4.5921475760604 | | 1969 | 5.0119725509852 | | 1968 | 4.1635478460279 | | 1967 | 3.1763689449481 | | 1966 | 3.4153672226345 | | 1965 | 1.958913232324 | | 1964 | 1.5955281337341 | | 1963 | 1.4339103409959 | | 1962 | 1.1301722367336 | | 1961 | 1.0447454518397 | | 1960 | 1.4083358192259 |
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