Year | Value | 2019 | 20.215003006615 | 2018 | 17.858784598192 | 2017 | 14.498514055731 | 2016 | 14.610731821716 | 2015 | 16.003859825482 | 2014 | 18.732953622593 | 2013 | 16.435472400223 | 2012 | 16.134692191801 | 2011 | 21.73463500223 | 2010 | 28.104338016904 | 2009 | 27.466546113361 | 2008 | 26.984591876418 | 2007 | 12.837871774975 | 2006 | 16.883676489874 | 2005 | 16.112082100923 | 2004 | 27.723739015437 | 2003 | 32.59507241966 | 2002 | 25.247281606787 | 2001 | 20.777209052633 | 2000 | 22.686582092787 | 1999 | 24.794858349341 | 1998 | 22.23266961389 | 1997 | 26.129752983085 | 1996 | 27.327143904227 | 1995 | 29.153006634115 | 1994 | 26.250665558103 | 1993 | 24.627837228545 | 1992 | 16.9239152927 | 1991 | 14.484701635198 | 1990 | 20.970410383443 | 1989 | 28.202579413853 | 1988 | 18.061631831438 | 1987 | 14.502527619957 | 1986 | 17.539112371965 | 1985 | 14.436133811488 | 1984 | 22.767437745022 | 1983 | 23.34107174962 | 1982 | 29.772329996361 | 1981 | 42.867991068901 | 1980 | 43.791885248791 | 1979 | 28.517796325784 | 1978 | 18.692670793129 | 1977 | 35.556908144709 | 1976 | 31.241140521103 |
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