| Year | Value | | 2022 | 8.8336988674945 | | 2021 | 1.9170650608926 | | 2020 | 0.05485681576061 | | 2019 | 1.6305226075434 | | 2018 | 1.7386086198818 | | 2017 | 1.4291074331931 | | 2016 | 0.054999541670474 | | 2015 | 0.52555228582088 | | 2014 | 0.19934382657075 | | 2013 | 1.7692008588191 | | 2012 | 2.59741386039 | | 2011 | 1.8028517194191 | | 2010 | 1.8011702213713 | | 2009 | 0.83926224679389 | | 2008 | 5.6474238057393 | | 2007 | 3.657495632841 | | 2006 | 2.4579244419586 | | 2005 | 2.4515013231648 | | 2004 | 3.5929759424951 | | 2003 | 5.544164217529 | | 2002 | 7.4807777070375 | | 2001 | 8.379665874922 | | 2000 | 8.9117441865877 | | 1999 | 6.1555875445156 | | 1998 | 7.8911668285668 | | 1997 | 8.359679907043 | | 1996 | 9.8644506154685 | | 1995 | 13.463729617867 | | 1994 | 20.99181804715 | | 1993 | 31.762130630593 | | 1992 | 209.93373118682 | | 1991 | 114.83293558975 | | 1990 | 552.08352891433 | | 1989 | 1,281.4434940488 | | 1988 | 198.75371286202 | | 1987 | 132.07272101483 | | 1986 | 95.886505210164 | | 1985 | 79.406381148187 | | 1984 | 53.671966910248 | | 1983 | 40.213491843693 | | 1982 | 30.112543595072 | | 1981 | 42.622952731824 |
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