| Year | Value | | 2016 | 27.418955113249 | | 2015 | 25.289897634136 | | 2014 | 23.460817252953 | | 2013 | 23.029072744929 | | 2012 | 24.450763982358 | | 2011 | 25.959125869771 | | 2010 | 24.706658386944 | | 2009 | 24.714659993282 | | 2008 | 25.427458471344 | | 2007 | 25.959754610612 | | 2006 | 25.28496540943 | | 2005 | 26.734742767378 | | 2004 | 25.774422993177 | | 2003 | 25.243417977878 |
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