| Year | Value | | 2022 | 26.980974934573 | | 2021 | 26.987862778108 | | 2020 | 27.212548475743 | | 2019 | 27.927712856751 | | 2018 | 29.891448446682 | | 2017 | 31.831258198891 | | 2016 | 33.895589577944 | | 2015 | 35.74848046034 | | 2014 | 38.129846721854 | | 2013 | 40.879064321149 | | 2012 | 42.850932313281 | | 2011 | 43.577661408791 | | 2010 | 43.361876260015 | | 2009 | 43.134980210182 | | 2008 | 43.397819128441 | | 2007 | 43.275161706195 | | 2006 | 43.510049412204 | | 2005 | 42.442653871896 | | 2004 | 41.816970728639 | | 2003 | 41.538477808295 | | 2002 | 41.480158956926 | | 2001 | 41.407008991561 | | 2000 | 41.416213809462 | | 1999 | 41.567322828793 | | 1998 | 41.61592645147 | | 1997 | 41.578751158464 | | 1996 | 41.526842655329 | | 1995 | 41.552513886859 | | 1994 | 41.595922459893 | | 1993 | 41.722313712905 | | 1992 | 41.688814870658 | | 1991 | 41.783049873689 |
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