| Year | Value | | 2021 | 15,963 | | 2020 | 15,848 | | 2019 | 15,718 | | 2018 | 15,618 | | 2017 | 15,559 | | 2016 | 15,650 | | 2015 | 15,711 | | 2014 | 15,506 | | 2013 | 15,582 | | 2012 | 15,438 | | 2011 | 15,680.563 | | 2010 | 15,590.12 | | 2009 | 15,044 | | 2008 | 15,041 | | 2007 | 15,011.52 | | 2006 | 14,472 | | 2005 | 14,272 | | 2004 | 14,395 | | 2003 | 14,387 | | 2002 | 13,856 | | 2001 | 13,868 | | 2000 | 13,868 | | 1999 | 13,875 | | 1998 | 13,862 | | 1997 | 13,853 | | 1996 | 13,837 | | 1995 | 13,856 |
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