| Year | Value | | 2021 | 34.107015842224 | | 2020 | 34.158098933075 | | 2019 | 34.206710249033 | | 2018 | 34.258049915945 | | 2017 | 34.293054141825 | | 2016 | 34.344109996284 | | 2015 | 34.395165850742 | | 2014 | 33.86668792856 | | 2013 | 33.786317971615 | | 2012 | 33.705948014671 | | 2011 | 33.625578057726 | | 2010 | 33.545208100781 | | 2009 | 33.645351618562 | | 2008 | 33.745495136342 | | 2007 | 33.845638654122 | | 2006 | 33.945782171902 | | 2005 | 34.045925689683 | | 2004 | 34.146069207463 | | 2003 | 34.246212725243 | | 2002 | 34.346356243023 | | 2001 | 34.446499760804 | | 2000 | 34.546643278584 | | 1999 | 34.839913889332 | | 1998 | 35.13318450008 | | 1997 | 35.426455110828 | | 1996 | 35.719725721576 | | 1995 | 36.012996332323 | | 1994 | 36.306266943071 | | 1993 | 36.599537553819 | | 1992 | 36.892808164567 | | 1991 | 37.186078775315 | | 1990 | 37.479349386063 |
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