| Year | Value | | 2021 | 79.192465829537 | | 2020 | 79.269252139127 | | 2019 | 79.25854724599 | | 2018 | 80.022261732785 | | 2017 | 80.088046820017 | | 2016 | 80.09856650739 | | 2015 | 80.105085750269 | | 2014 | 80.304996851502 | | 2013 | 80.377115975849 | | 2012 | 80.383783383339 | | 2011 | 80.375041671297 | | 2010 | 80.439233988962 | | 2009 | 78.076564062674 | | 2008 | 78.101789087676 | | 2007 | 78.318183501871 | | 2006 | 78.481497944216 | | 2005 | 78.633181464607 | | 2004 | 78.775604696818 | | 2003 | 78.898173871171 | | 2002 | 79.07134126014 | | 2001 | 79.447938659851 | | 2000 | 79.784161203097 | | 1999 | 79.666370337445 | | 1998 | 79.760640071119 | | 1997 | 79.894729043968 | | 1996 | 79.813905248731 | | 1995 | 80.448383153684 | | 1994 | 82.102085416898 | | 1993 | 82.13764492351 | | 1992 | 82.032448049783 |
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