| Year | Value | | 2021 | 39.922268642229 | | 2020 | 39.048563128449 | | 2019 | 31.777147347289 | | 2010 | 33.862521232019 | | 2008 | 43.799987249558 | | 2007 | 42.97866113788 | | 2006 | 49.686968034687 | | 2005 | 51.764623048055 | | 2004 | 59.415667285826 | | 2003 | 62.588195379812 | | 2002 | 63.935460982102 | | 2001 | 58.989141587714 | | 2000 | 64.573319841471 | | 1999 | 64.068109789613 | | 1998 | 66.351443434327 | | 1997 | 59.882429691316 | | 1996 | 65.197880383909 | | 1995 | 66.183643207483 | | 1994 | 66.541210004416 | | 1993 | 63.681538233854 | | 1992 | 61.656922988271 | | 1991 | 64.911430440788 | | 1990 | 52.620580954591 |
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