| Year | Value | | 2021 | 0.94660549827608 | | 2020 | 0.92253218774316 | | 2019 | 0.95062310231061 | | 2018 | 0.90726806372661 | | 2017 | 0.96288288944736 | | 2016 | 1.1538491432022 | | 2015 | 1.0550109095807 | | 2014 | 1.0800024456843 | | 2013 | 0.94758782218642 | | 2012 | 1.1580952548775 | | 2011 | 1.3672582745875 | | 2010 | 1.3661660491861 | | 2009 | 1.3472272968492 | | 2008 | 1.2892006116247 | | 2007 | 1.1578718956278 | | 2006 | 1.0582578193184 | | 2005 | 1.0860314390825 | | 2004 | 1.0567953515411 | | 2003 | 0.96565352275994 | | 2002 | 0.94741475385006 | | 2001 | 0.92244324877558 | | 2000 | 0.96821824631405 | | 1999 | 1.0051953919133 | | 1998 | 0.96903847003224 | | 1997 | 1.0233140947752 | | 1996 | 1.0566731559593 | | 1995 | 1.1109887555213 | | 1994 | 0.76128635002379 | | 1993 | 1.2878344409628 | | 1992 | 1.9010332579916 | | 1991 | 1.84366019825 | | 1990 | 1.5994939737154 | | 1989 | 1.7099406249765 | | 1988 | 2.8561943741753 | | 1987 | 3.6991620682608 | | 1986 | 4.8370724955303 | | 1985 | 4.7225439612509 | | 1984 | 4.2859822433412 | | 1983 | 5.4363796650015 | | 1982 | 6.5250379362671 | | 1981 | 5.2894211576846 | | 1980 | 4.7511312217195 | | 1979 | 5.4187192118227 | | 1978 | 6.3157894736842 | | 1977 | 9.8360655737705 | | 1976 | 14.634146341463 | | 1975 | 14.285714285714 | | 1974 | 25 | | 1973 | 27.272727272727 | | 1972 | 22.222222222222 |
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