| Year | Value | | 2021 | 33.727367833535 | | 2020 | 33.793091386095 | | 2019 | 33.858818385247 | | 2018 | 33.924540240233 | | 2017 | 33.990267239384 | | 2016 | 34.055994238535 | | 2015 | 34.121716093521 | | 2014 | 34.184721829265 | | 2013 | 34.247727565009 | | 2012 | 34.310733300754 | | 2011 | 34.373739036498 | | 2010 | 34.436744772242 | | 2009 | 34.510719925924 | | 2008 | 34.584695079606 | | 2007 | 34.658670233288 | | 2006 | 34.73264538697 | | 2005 | 34.806620540652 | | 2004 | 34.880595694334 | | 2003 | 34.954570848016 | | 2002 | 35.028546001698 | | 2001 | 35.102521155379 | | 2000 | 35.176496309061 | | 1999 | 35.290197793153 | | 1998 | 35.403899277245 | | 1997 | 35.517600761337 | | 1996 | 35.631302245428 | | 1995 | 35.74500372952 | | 1994 | 35.858705213612 | | 1993 | 35.972406697703 | | 1992 | 36.086108181795 | | 1991 | 36.199809665886 | | 1990 | 36.313511149978 |
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