| Year | Value | | 2022 | 9.6452598128063 | | 2021 | 1.2238250101985 | | 2020 | -1.247983555814 | | 2019 | 0.25300752203816 | | 2018 | 0.62562141345364 | | 2017 | 1.1212545203142 | | 2016 | 0.82565397839097 | | 2015 | -1.7358880476528 | | 2014 | -1.3122609640551 | | 2013 | 0.92126945425699 | | 2012 | 1.5015269617776 | | 2011 | 3.3298532335065 | | 2010 | 4.7129890776039 | | 2009 | 1.2100726919781 | | 2008 | 4.1527970811029 | | 2007 | 2.8950032151658 | | 2006 | 3.1959468414454 | | 2005 | 3.5450727333508 | | 2004 | 2.8988481075817 | | 2003 | 3.5306502776555 | | 2002 | 3.6293587187887 | | 2001 | 3.3739683221387 | | 2000 | 3.1511816249383 | | 1999 | 2.6366330602198 | | 1998 | 4.7662257239764 | | 1997 | 5.5360026677348 | | 1996 | 8.1945521763273 | | 1995 | 8.9345141596152 | | 1994 | 10.874075680913 | | 1993 | 14.411264443935 | | 1992 | 15.877073792392 | | 1991 | 19.455845644574 | | 1990 | 20.433499109463 | | 1989 | 13.655563872361 | | 1988 | 13.528858321505 | | 1987 | 16.396863163536 | | 1986 | 23.015450820501 | | 1985 | 19.314692940664 | | 1984 | 18.456813205019 | | 1983 | 20.179481289214 | | 1982 | 20.991088622002 | | 1981 | 24.506067597797 | | 1980 | 24.675893973623 | | 1979 | 19.094174680877 | | 1978 | 12.572425672444 | | 1977 | 12.369797087508 | | 1976 | 13.024279458795 | | 1975 | 13.628761782176 | | 1974 | 26.560846586735 | | 1973 | 15.384624070213 | | 1972 | 4.3312012320335 | | 1971 | 3.2894707223033 | | 1970 | 2.8416706788412 | | 1969 | 2.6389186883548 | | 1968 | 0.13906058350775 | | 1967 | 1.841357027506 | | 1966 | 4.903415961306 | | 1965 | 3.220872469971 | | 1964 | 0.61730297851252 | | 1963 | 3.1846627279161 | | 1962 | 0.47542829104991 | | 1961 | 2.1035793499702 | | 1960 | 1.4778475849338 |
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