| Year | Value | | 2020 | 0.34063735520074 | | 2019 | 0.34747317507088 | | 2018 | 0.33750261564527 | | 2017 | 0.3633676917673 | | 2016 | 0.34923804475999 | | 2015 | 0.35539589220884 | | 2014 | 0.36152213578771 | | 2013 | 0.45289073687479 | | 2012 | 0.45941686436176 | | 2011 | 0.46619260059104 | | 2010 | 0.47330236583568 | | 2009 | 0.48090949603891 | | 2008 | 0.51160815652233 | | 2007 | 0.51834249150272 | | 2006 | 0.52340973846643 | | 2005 | 0.62454870350895 | | 2004 | 0.63362151739681 | | 2003 | 0.67046562806383 | | 2002 | 0.69765245316069 | | 2001 | 0.34052754527314 | | 2000 | 0.22835975796269 | | 1999 | 0.23357721663242 | | 1998 | 0.3576846701284 | | 1997 | 0.98237507204602 | | 1996 | 0.9435000707625 | | 1995 | 0.4422156774302 | | 1994 | 0.31604463814469 | | 1993 | 0.31701629336941 | | 1992 | 0.50602677893714 | | 1991 | 0.31057058027007 |
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