Year | Value | 2021 | 16.110189427506 | 2020 | 13.185874431575 | 2019 | 14.5254040571 | 2018 | 14.286371309979 | 2017 | 13.174341651093 | 2016 | 13.787547642923 | 2015 | 14.919651317912 | 2014 | 16.720926678532 | 2013 | 16.433006693027 | 2012 | 16.546687102767 | 2011 | 15.968895145209 | 2010 | 15.466571757043 | 2009 | 14.456526808392 | 2008 | 16.512170920242 | 2007 | 16.40746835032 | 2006 | 15.669987601514 | 2005 | 14.104742192392 | 2004 | 13.6633689429 | 2003 | 13.411521163568 | 2002 | 12.487142627315 | 2001 | 12.897105633687 | 2000 | 12.608647499225 | 1999 | 12.994189298183 | 1998 | 14.234804964757 | 1997 | 14.398760530648 | 1996 | 14.199814167515 | 1995 | 13.684757572986 | 1994 | 12.972144168636 | 1993 | 12.165422062863 | 1992 | 11.983052381058 | 1991 | 11.027944271671 | 1990 | 10.723895209151 | 1989 | 7.9216590244156 | 1988 | 9.6635826761263 | 1987 | 9.9744158534231 | 1986 | 13.382109848495 | 1985 | 14.962994037624 | 1984 | 13.040409728783 | 1983 | 11.897730920354 | 1982 | 14.792993420102 | 1981 | 15.116329865085 | 1980 | 17.961713769142 | 1979 | 13.806882854712 | 1978 | 12.493021604855 | 1977 | 11.671674300445 | 1976 | 11.229074340504 | 1975 | 11.557731547666 | 1974 | 11.000860633556 | 1973 | 10.811253441313 | 1972 | 12.653590016203 |
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