| Year | Value | | 2020 | 0.75095478536997 | | 2019 | 0.76827057172501 | | 2018 | 0.77781073445802 | | 2017 | 0.80378713879337 | | 2016 | 0.77121697282216 | | 2015 | 0.77775735952902 | | 2014 | 0.79326286514881 | | 2013 | 0.79269508167674 | | 2012 | 0.78224038246953 | | 2011 | 0.76312804690095 | | 2010 | 0.76230534589045 | | 2009 | 0.77254613406932 | | 2008 | 0.80503075217473 | | 2007 | 0.80979122425394 | | 2006 | 0.81634049328735 | | 2005 | 0.71186199368816 | | 2004 | 0.68800145694426 | | 2003 | 0.65495384017149 | | 2002 | 0.66569700989 | | 2001 | 0.59948624029207 | | 2000 | 0.60941316994096 | | 1999 | 0.54092832167677 | | 1998 | 0.64415072582632 | | 1997 | 0.65946518302481 | | 1996 | 0.56406351355163 | | 1995 | 0.33306592897322 | | 1994 | 0.6305821680094 | | 1993 | 0.5953792615511 | | 1992 | 0.60327093500962 |
|