| Year | Value | | 2021 | 32.812616648003 | | 2020 | 32.920865994774 | | 2019 | 33.029115341545 | | 2018 | 33.137364688317 | | 2017 | 33.245614035088 | | 2016 | 33.353863381859 | | 2015 | 33.46211272863 | | 2014 | 33.717431877566 | | 2013 | 33.972751026502 | | 2012 | 34.228070175439 | | 2011 | 34.483389324375 | | 2010 | 34.738708473311 | | 2009 | 35.192795819336 | | 2008 | 35.64688316536 | | 2007 | 36.100970511385 | | 2006 | 36.55505785741 | | 2005 | 37.009145203434 | | 2004 | 37.463232549459 | | 2003 | 37.917319895483 | | 2002 | 38.371407241508 | | 2001 | 38.825494587533 | | 2000 | 39.279581933557 | | 1999 | 39.813363195222 | | 1998 | 40.347144456887 | | 1997 | 40.880925718552 | | 1996 | 41.414706980217 | | 1995 | 41.948488241881 | | 1994 | 42.482269503546 | | 1993 | 43.016050765211 | | 1992 | 43.549832026876 | | 1991 | 44.08361328854 | | 1990 | 44.617394550205 |
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