| Year | Value | | 2021 | 56.647689695236 | | 2020 | 56.834927160604 | | 2019 | 57.022164625972 | | 2018 | 57.20940209134 | | 2017 | 57.396639556707 | | 2016 | 57.583787648583 | | 2015 | 57.76950576459 | | 2014 | 57.969058897131 | | 2013 | 58.168612029672 | | 2012 | 58.368165162213 | | 2011 | 58.567718294754 | | 2010 | 58.767271427295 | | 2009 | 58.94852086871 | | 2008 | 59.129770310126 | | 2007 | 59.311019751542 | | 2006 | 59.492269192957 | | 2005 | 59.673518634373 | | 2004 | 59.854768075789 | | 2003 | 60.036017517204 | | 2002 | 60.21726695862 | | 2001 | 60.398516400036 | | 2000 | 60.579765841451 | | 1999 | 60.767012244168 | | 1998 | 60.954258646885 | | 1997 | 61.141505049602 | | 1996 | 61.328751452319 | | 1995 | 61.515997855036 | | 1994 | 61.703244257753 | | 1993 | 61.89049066047 | | 1992 | 62.077737063187 | | 1991 | 62.264983465904 | | 1990 | 62.452229868621 |
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