| Year | Value | | 2020 | 0.088435587718596 | | 2019 | 0.089969279989348 | | 2018 | 0.096656557618125 | | 2017 | 0.094061564234407 | | 2016 | 0.0984295918725 | | 2015 | 0.10059577232772 | | 2014 | 0.10273006397828 | | 2013 | 0.10475832764828 | | 2012 | 0.10680983004732 | | 2011 | 0.11114406276549 | | 2010 | 0.115792114557 | | 2009 | 0.11911664497459 | | 2008 | 0.12048657297631 | | 2007 | 0.12537832910808 | | 2006 | 0.13144836379649 | | 2005 | 1.0400827073769 | | 2003 | 1.0956766789602 | | 2002 | 1.1024304917575 | | 2001 | 1.1304476271151 | | 2000 | 1.1638553095079 | | 1999 | 0.42614572897453 | | 1998 | 1.1902181074682 | | 1997 | 2.0740061975076 | | 1996 | 2.2464911340185 | | 1995 | 2.2118627465437 | | 1992 | 0.22243229716955 | | 1991 | 0.59072537531737 |
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