| Year | Value | | 2022 | 1.5078235912053 | | 2021 | 1.885371695382 | | 2020 | 2.0206047275134 | | 2019 | 1.4199869433401 | | 2018 | 1.3353365463557 | | 2017 | 0.9879644152518 | | 2016 | 0.92958455701374 | | 2015 | 0.84028527415069 | | 2014 | 0.98075949386584 | | 2013 | 0.93018222970771 | | 2012 | 0.85072600767818 | | 2011 | 0.82655322493467 | | 2010 | 0.89190227344571 | | 2009 | 0.70542260842237 | | 2008 | 0.66492166187923 | | 2007 | 0.66895389816373 | | 2006 | 0.80946727177905 | | 2005 | 0.94623188119204 | | 2004 | 1.3624211148071 | | 2003 | 1.2809422111685 | | 2002 | 1.2736356416932 | | 2001 | 1.2421712394688 | | 2000 | 1.2844579069583 | | 1999 | 1.2458693907837 | | 1998 | 1.1392116655275 | | 1997 | 1.1027413923645 | | 1996 | 1.1116816711826 | | 1995 | 1.4604823460569 | | 1994 | 3.3035017118145 | | 1993 | 2.870883870251 | | 1992 | 2.9684454251309 | | 1991 | 2.6120320848834 | | 1990 | 5.8612975391499 | | 1989 | 5.9434914228053 | | 1988 | 5.3090332805071 | | 1987 | 6.1832061068702 | | 1986 | 5.655737704918 | | 1985 | 5.7657657657658 | | 1984 | 7.0731707317073 | | 1983 | 6.232 | | 1982 | 4.9240506329114 | | 1981 | 4.2804878048781 | | 1980 | 3.8333333333333 |
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