| Year | Value | | 2022 | 41.853481122282 | | 2021 | 41.46458042642 | | 2020 | 41.180369777132 | | 2019 | 41.140575124769 | | 2018 | 40.436721424824 | | 2017 | 39.809978695194 | | 2016 | 39.297316742732 | | 2015 | 39.212046591456 | | 2014 | 39.021949927131 | | 2013 | 38.764460949488 | | 2012 | 38.391997833986 | | 2011 | 38.028400598985 | | 2010 | 37.65980865001 | | 2009 | 37.106956804779 | | 2008 | 36.557128172218 | | 2007 | 36.049782530243 | | 2006 | 35.57180863847 | | 2005 | 35.149864489398 | | 2004 | 34.66624444102 | | 2003 | 34.264962309933 | | 2002 | 33.909343997552 | | 2001 | 33.570095435779 | | 2000 | 33.260360238791 | | 1999 | 33.045020521612 | | 1998 | 32.917982864469 | | 1997 | 32.772656081313 | | 1996 | 32.679495355547 | | 1995 | 32.612527106502 | | 1994 | 32.571381035498 | | 1993 | 32.544769123177 | | 1992 | 32.513146848434 | | 1991 | 32.50490565339 |
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