| Year | Value | | 2020 | 0.24658046829946 | | 2019 | 0.26154222623762 | | 2018 | 0.27809987654784 | | 2017 | 0.28599558279822 | | 2016 | 0.30530492282909 | | 2015 | 0.3161956565065 | | 2014 | 0.32753854781318 | | 2013 | 0.33940183820036 | | 2012 | 0.35160417808048 | | 2011 | 0.36418711890025 | | 2010 | 0.37750500308524 | | 2009 | 0.39237610843278 | | 2008 | 0.39580202477473 | | 2007 | 0.41180500826956 | | 2006 | 0.42825268621497 | | 2005 | 0.44505466383909 | | 2004 | 0.46161751353766 | | 2003 | 0.58293489484153 | | 2002 | 0.71208863336259 | | 2001 | 0.73772616118098 | | 2000 | 0.76391123882821 | | 1999 | 0.78661469081597 | | 1998 | 0.80795817727445 | | 1997 | 0.82944605625447 | | 1996 | 0.85103076476215 | | 1995 | 0.87165422159194 | | 1994 | 0.62051604441189 | | 1993 | 0.63521101709988 | | 1992 | 0.65043082912044 | | 1991 | 0.66666388890046 |
|