Year | Value | 2021 | 18.270791558882 | 2020 | 16.876329394276 | 2019 | 18.315941645175 | 2018 | 18.520786854229 | 2017 | 18.3381224193 | 2016 | 18.606657823486 | 2015 | 18.493883079917 | 2014 | 18.168817949332 | 2013 | 17.899869406471 | 2012 | 17.867316914181 | 2011 | 17.839164269943 | 2010 | 18.057302365375 | 2009 | 17.997151118247 | 2008 | 19.407959215411 | 2007 | 20.074751116628 | 2006 | 20.893860031577 | 2005 | 21.148998492558 | 2004 | 20.634255108071 | 2003 | 20.665570282419 | 2002 | 20.503269512878 | 2001 | 19.94939686591 | 2000 | 20.095838768773 | 1999 | 20.838842986001 | 1998 | 20.502075070441 | 1997 | 19.801704632469 | 1996 | 20.102969511294 | 1995 | 19.42547020541 |
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