| Year | Value | | 2021 | 35.427624468622 | | 2020 | 35.420419338569 | | 2019 | 35.436270624685 | | 2018 | 35.388716766338 | | 2017 | 35.356293681101 | | 2016 | 35.127891058434 | | 2015 | 34.900208948771 | | 2014 | 34.673526148171 | | 2013 | 34.156901971992 | | 2012 | 33.931123178051 | | 2011 | 33.958273792512 | | 2010 | 33.978993998285 | | 2009 | 34.005430122892 | | 2008 | 33.773935410117 | | 2007 | 33.788225207202 | | 2006 | 33.831094598457 | | 2005 | 33.380965990283 | | 2004 | 33.223778222349 | | 2003 | 32.837953701057 | | 2002 | 32.659331237496 | | 2001 | 32.673621034581 | | 2000 | 32.673621034581 | | 1999 | 32.637896541869 | | 1998 | 32.487853672478 | | 1997 | 32.595027150614 | | 1996 | 32.759359817091 | | 1995 | 32.737925121463 | | 1994 | 31.93769648471 | | 1993 | 32.459274078308 | | 1992 | 32.073449557016 |
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