| Year | Value | | 2020 | 0.080502876587334 | | 2019 | 0.082382643864249 | | 2018 | 0.086561905635621 | | 2017 | 0.087809074972107 | | 2016 | 0.092572916255978 | | 2015 | 0.095905067683717 | | 2014 | 0.098881666014813 | | 2013 | 0.10189549270747 | | 2012 | 0.10488565824413 | | 2011 | 0.1077720901271 | | 2010 | 0.11049669249856 | | 2009 | 0.11301960637895 | | 2008 | 0.11334406942098 | | 2007 | 0.1157496070827 | | 2006 | 0.11822476699242 | | 2005 | 0.12069203496207 | | 2004 | 0.1232453779622 | | 2003 | 0.093823582145464 | | 2002 | 0.12849406012844 | | 2001 | 0.13115406154917 | | 2000 | 0.074169201591647 | | 1999 | 0.075565536813238 | | 1998 | 0.076962664654366 | | 1997 | 0.078377921376409 | | 1996 | 0.14504056850629 | | 1995 | 0.16327488047258 | | 1994 | 0.15650469805762 | | 1993 | 0.74684294550078 | | 1992 | 0.76829014569547 | | 1991 | 1.0185991503629 |
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