| Year | Value | | 2022 | 11.245823902723 | | 2021 | 11.008633384352 | | 2020 | 10.838838203497 | | 2019 | 10.973234264266 | | 2018 | 10.836291865491 | | 2017 | 10.800909082087 | | 2016 | 10.7127392444 | | 2015 | 10.585385680583 | | 2014 | 10.703915132154 | | 2013 | 10.80564162783 | | 2012 | 10.99302415294 | | 2011 | 10.132553381552 | | 2010 | 9.3218312017697 | | 2009 | 10.086088664371 | | 2008 | 10.862042314141 | | 2007 | 11.491387009626 | | 2006 | 12.325989900214 | | 2005 | 13.205439448715 | | 2004 | 14.134534224615 | | 2003 | 15.102184378688 | | 2002 | 21.236456471684 | | 2001 | 27.589819121296 | | 2000 | 25.82352836533 | | 1999 | 23.973141499918 | | 1998 | 22.075559713839 | | 1997 | 20.170943651626 | | 1996 | 18.288361458894 | | 1995 | 16.420522183677 | | 1994 | 14.885977638455 | | 1993 | 13.312237715492 | | 1992 | 12.888768491211 | | 1991 | 12.665453595791 |
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