Year | Value | 2021 | 16.213329840949 | 2020 | 15.389724540237 | 2019 | 15.409521830774 | 2018 | 15.434207610281 | 2017 | 16.012223653548 | 2016 | 15.613291377328 | 2015 | 15.706679439423 | 2014 | 15.560386438262 | 2013 | 15.376949781748 | 2012 | 14.926094752515 | 2011 | 14.807831649722 | 2010 | 14.27142169528 | 2009 | 13.935468616282 | 2008 | 15.484285246767 | 2007 | 15.978072337595 | 2006 | 15.891914677049 | 2005 | 15.459362588098 | 2004 | 14.781782000631 | 2003 | 14.748886937099 | 2002 | 15.020390739216 | 2001 | 16.205698482052 | 2000 | 16.8496853768 | 1999 | 16.401959349976 | 1998 | 16.246805515561 | 1997 | 15.803318326185 | 1996 | 15.384168060298 | 1995 | 15.085241108802 | 1994 | 14.5724439862 | 1993 | 14.073639919862 | 1992 | 14.109465032167 | 1991 | 14.505976507204 | 1990 | 14.497391919089 | 1989 | 14.565230794024 | 1988 | 14.581249946645 | 1987 | 14.736915245837 | 1986 | 14.372276419075 | 1985 | 14.373530460428 | 1984 | 14.104718151792 | 1983 | 14.197930654988 | 1982 | 14.941375293535 | 1981 | 15.072073696285 | 1980 | 14.755648366123 | 1979 | 14.508323171775 | 1978 | 14.300661317645 | 1977 | 14.396635395579 | 1976 | 13.924329017573 | 1975 | 13.850298072385 | 1974 | 14.143241744264 | 1973 | 13.658115590546 | 1972 | 13.996253113756 |
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