| Year | Value | | 2021 | 58.024318977325 | | 2020 | 58.176959366915 | | 2019 | 58.329599756506 | | 2018 | 58.482240146097 | | 2017 | 58.634880535687 | | 2016 | 58.787520925278 | | 2015 | 59.242794095267 | | 2014 | 58.928339674327 | | 2013 | 58.613885253386 | | 2012 | 58.299430832446 | | 2011 | 57.984976411505 | | 2010 | 57.670521990565 | | 2009 | 57.896880231319 | | 2008 | 58.123238472074 | | 2007 | 58.349596712829 | | 2006 | 58.575954953584 | | 2005 | 58.802313194339 | | 2004 | 59.028671435094 | | 2003 | 59.255029675848 | | 2002 | 59.481387916603 | | 2001 | 59.707746157358 | | 2000 | 59.934104398113 | | 1999 | 60.216298889058 | | 1998 | 60.498493380003 | | 1997 | 60.780687870948 | | 1996 | 61.062882361893 | | 1995 | 61.345076852838 | | 1994 | 61.627271343783 | | 1993 | 61.909465834728 | | 1992 | 62.191660325673 | | 1991 | 62.473854816618 | | 1990 | 62.756049307564 |
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